@ifinfo
@format
START-INFO-DIR-ENTRY
-* Stabs: (stabs). The "stabs" debugging information format.
+* Stabs:: The "stabs" debugging information format.
END-INFO-DIR-ENTRY
@end format
@end ifinfo
@ifinfo
-This document describes GNU stabs (debugging symbol tables) in a.out files.
+This document describes the stabs debugging symbol tables.
Copyright 1992 Free Software Foundation, Inc.
Contributed by Cygnus Support. Written by Julia Menapace.
@node Top
@top The "stabs" representation of debugging information
-This document describes the GNU stabs debugging format in a.out files.
+This document describes the stabs debugging format.
@menu
-* Overview:: Overview of stabs
-* Program structure:: Encoding of the structure of the program
-* Simple types::
-* Example:: A comprehensive example in C
-* Variables::
-* Aggregate types::
-* Symbol tables:: Symbol information in symbol tables
-* GNU Cplusplus stabs::
-
-Appendixes:
-* Example2.c:: Source code for extended example
-* Example2.s:: Assembly code for extended example
-* Quick reference:: Various refernce tables
-* Expanded reference:: Reference information by stab type
-* Questions:: Questions and anomolies
-* xcoff-differences:: Differences between GNU stabs in a.out
+* Overview:: Overview of stabs
+* Program structure:: Encoding of the structure of the program
+* Constants:: Constants
+* Example:: A comprehensive example in C
+* Variables::
+* Types:: Type definitions
+* Symbol Tables:: Symbol information in symbol tables
+* Cplusplus:: Appendixes:
+* Example2.c:: Source code for extended example
+* Example2.s:: Assembly code for extended example
+* Stab Types:: Symbol types in a.out files
+* Symbol Descriptors:: Table of Symbol Descriptors
+* Type Descriptors:: Table of Symbol Descriptors
+* Expanded reference:: Reference information by stab type
+* Questions:: Questions and anomolies
+* xcoff-differences:: Differences between GNU stabs in a.out
and GNU stabs in xcoff
-* Sun-differences:: Differences between GNU stabs and Sun
+* Sun-differences:: Differences between GNU stabs and Sun
native stabs
+* Stabs-in-elf:: Stabs in an ELF file.
@end menu
@end ifinfo
the University of California at Berkeley, for the @code{pdx} Pascal
debugger; the format has spread widely since then.
+This document is one of the few published sources of documentation on
+stabs. It is believed to be completely comprehensive for stabs used by
+C. The lists of symbol descriptors (@pxref{Symbol Descriptors}) and
+type descriptors (@pxref{Type Descriptors}) are believed to be completely
+comprehensive. There are known to be stabs for C++ and COBOL which are
+poorly documented here. Stabs specific to other languages (e.g. Pascal,
+Modula-2) are probably not as well documented as they should be.
+
+Other sources of information on stabs are @cite{dbx and dbxtool
+interfaces}, 2nd edition, by Sun, circa 1988, and @cite{AIX Version 3.2
+Files Reference}, Fourth Edition, September 1992, "dbx Stabstring
+Grammar" in the a.out section, page 2-31. This document is believed to
+incorporate the information from those two sources except where it
+explictly directs you to them for more information.
+
@menu
-* Flow:: Overview of debugging information flow
-* Stabs format:: Overview of stab format
-* C example:: A simple example in C source
-* Assembly code:: The simple example at the assembly level
+* Flow:: Overview of debugging information flow
+* Stabs Format:: Overview of stab format
+* C example:: A simple example in C source
+* Assembly code:: The simple example at the assembly level
@end menu
@node Flow
table. Debuggers use the symbol and string tables in the executable as
a source of debugging information about the program.
-@node Stabs format
+@node Stabs Format
@section Overview of stab format
There are three overall formats for stab assembler directives
differentiated by the first word of the stab. The name of the directive
describes what combination of four possible data fields will follow. It
is either @code{.stabs} (string), @code{.stabn} (number), or
-@code{.stabd} (dot).
+@code{.stabd} (dot). IBM's xcoff uses @code{.stabx} (and some other
+directives such as @code{.file} and @code{.bi}) instead of
+@code{.stabs}, @code{.stabn} or @code{.stabd}.
The overall format of each class of stab is:
@example
.stabs "@var{string}",@var{type},0,@var{desc},@var{value}
-.stabn @var{type},0,@var{desc},@var{value}
-.stabd @var{type},0,@var{desc}
-@end example
-
-In general, in @code{.stabs} the @var{string} field contains name and type
-information. For @code{.stabd} the value field is implicit and has the value
-of the current file location. Otherwise the value field often
-contains a relocatable address, frame pointer offset, or register
-number, that maps to the source code element described by the stab.
-
-The real key to decoding the meaning of a stab is the number in its type
-field. Each possible type number defines a different stab type. The
-stab type further defines the exact interpretation of, and possible
-values for, any remaining @code{"@var{string}"}, @var{desc}, or
-@var{value} fields present in the stab. Table A (@pxref{Stab
-types,,Table A: Symbol types from stabs}) lists in numeric order
-the possible type field values for stab directives. The reference
-section that follows Table A describes the meaning of the fields for
-each stab type in detail. The examples that follow this overview
-introduce the stab types in terms of the source code elements they
-describe.
+.stabx "@var{string}",@var{value},@var{type},@var{sdb-type}
+.stabn @var{type},0,@var{desc},@var{value}
+.stabd @var{type},0,@var{desc}
+@end example
+
+@c what is the correct term for "current file location"? My AIX
+@c assembler manual calls it "the value of the current location counter".
+For @code{.stabn} and @code{.stabd}, there is no string (the
+@code{n_strx} field is zero, @pxref{Symbol Tables}). For @code{.stabd}
+the value field is implicit and has the value of the current file
+location. The @var{sdb-type} field to @code{.stabx} is unused for stabs
+and can always be set to 0.
+
+The number in the type field gives some basic information about what
+type of stab this is (or whether it @emph{is} a stab, as opposed to an
+ordinary symbol). Each possible type number defines a different stab
+type. The stab type further defines the exact interpretation of, and
+possible values for, any remaining @code{"@var{string}"}, @var{desc}, or
+@var{value} fields present in the stab. @xref{Stab Types}, for a list
+in numeric order of the possible type field values for stab directives.
For @code{.stabs} the @code{"@var{string}"} field holds the meat of the
debugging information. The generally unstructured nature of this field
The overall format is of the @code{"@var{string}"} field is:
@example
-"@var{name}@r{[}:@var{symbol_descriptor}@r{]}
- @r{[}@var{type_number}@r{[}=@var{type_descriptor} @r{@dots{}]]}"
+"@var{name}:@var{symbol-descriptor} @var{type-information}"
@end example
@var{name} is the name of the symbol represented by the stab.
+@var{name} can be omitted, which means the stab represents an unnamed
+object. For example, @samp{:t10=*2} defines type 10 as a pointer to
+type 2, but does not give the type a name. Omitting the @var{name}
+field is supported by AIX dbx and GDB after about version 4.8, but not
+other debuggers. GCC sometimes uses a single space as the name instead
+of omitting the name altogether; apparently that is supported by most
+debuggers.
The @var{symbol_descriptor} following the @samp{:} is an alphabetic
character that tells more specifically what kind of symbol the stab
represents. If the @var{symbol_descriptor} is omitted, but type
information follows, then the stab represents a local variable. For a
-list of symbol_descriptors, see @ref{Symbol descriptors,,Table C: Symbol
+list of symbol descriptors, see @ref{Symbol Descriptors,,Table C: Symbol
descriptors}.
+The @samp{c} symbol descriptor is an exception in that it is not
+followed by type information. @xref{Constants}.
+
Type information is either a @var{type_number}, or a
@samp{@var{type_number}=}. The @var{type_number} alone is a type
reference, referring directly to a type that has already been defined.
Descriptors,,Table D: Type Descriptors}, for a list of
@var{type_descriptor} values.
-@c FIXME! "too long" below introduced at J Gilmore's request; used to
-@c say "more than 80 chars". Why is vaguer better?
-All this can make the @code{"@var{string}"} field quite long. When the
-@code{"@var{string}"} part of a stab is too long, the compiler splits
-the @code{.stabs} directive into two @code{.stabs} directives. Both
-stabs duplicate exactly all but the @code{"@var{string}"} field. The
-@code{"@var{string}"} field of the first stab contains the first part of
-the overlong string, marked as continued with a double-backslash at the
-end. The @code{"@var{string}"} field of the second stab holds the
-second half of the overlong string.
+There is an AIX extension for type attributes. Following the @samp{=}
+is any number of type attributes. Each one starts with @samp{@@} and
+ends with @samp{;}. Debuggers, including AIX's dbx, skip any type
+attributes they do not recognize. GDB 4.9 does not do this---it will
+ignore the entire symbol containing a type attribute. Hopefully this
+will be fixed in the next GDB release. Because of a conflict with C++
+(@pxref{Cplusplus}), new attributes should not be defined which begin
+with a digit, @samp{(}, or @samp{-}; GDB may be unable to distinguish
+those from the C++ type descriptor @samp{@@}. The attributes are:
+
+@table @code
+@item a@var{boundary}
+@var{boundary} is an integer specifying the alignment. I assume it
+applies to all variables of this type.
+
+@item s@var{size}
+Size in bits of a variable of this type.
+
+@item p@var{integer}
+Pointer class (for checking). Not sure what this means, or how
+@var{integer} is interpreted.
+
+@item P
+Indicate this is a packed type, meaning that structure fields or array
+elements are placed more closely in memory, to save memory at the
+expense of speed.
+@end table
+
+All this can make the @code{"@var{string}"} field quite long. All
+versions of GDB, and some versions of DBX, can handle arbitrarily long
+strings. But many versions of DBX cretinously limit the strings to
+about 80 characters, so compilers which must work with such DBX's need
+to split the @code{.stabs} directive into several @code{.stabs}
+directives. Each stab duplicates exactly all but the
+@code{"@var{string}"} field. The @code{"@var{string}"} field of
+every stab except the last is marked as continued with a
+double-backslash at the end. Removing the backslashes and concatenating
+the @code{"@var{string}"} fields of each stab produces the original,
+long string.
@node C example
@section A simple example in C source
@chapter Encoding for the structure of the program
@menu
-* Source file:: The path and name of the source file
-* Line numbers::
-* Procedures::
-* Block structure::
+* Main Program:: Indicate what the main program is
+* Source Files:: The path and name of the source file
+* Line Numbers::
+* Procedures::
+* Block Structure::
@end menu
-@node Source file
-@section The path and name of the source file
-
-@table @strong
-@item Directive:
-@code{.stabs}
-@item Type:
-@code{N_SO}
-@end table
-
-The first stabs in the .s file contain the name and path of the source
-file that was compiled to produce the .s file. This information is
-contained in two records of stab type N_SO (100).
-
-@example
- .stabs "path_name", N_SO, NIL, NIL, Code_address_of_program_start
- .stabs "file_name:", N_SO, NIL, NIL, Code_address_of_program_start
-@end example
-
-@example
-2 .stabs "/cygint/s1/users/jcm/play/",100,0,0,Ltext0
-3 .stabs "hello.c",100,0,0,Ltext0
-4 .text
-5 Ltext0:
-@end example
-
-@node Line numbers
+@node Main Program
+@section Main Program
+
+Most languages allow the main program to have any name. The
+@code{N_MAIN} stab type is used for a stab telling the debugger what
+name is used in this program. Only the name is significant; it will be
+the name of a function which is the main program. Most C compilers do
+not use this stab; they expect the debugger to simply assume that the
+name is @samp{main}, but some C compilers emit an @code{N_MAIN} stab for
+the @samp{main} function.
+
+@node Source Files
+@section The path and name of the source files
+
+Before any other stabs occur, there must be a stab specifying the source
+file. This information is contained in a symbol of stab type
+@code{N_SO}; the string contains the name of the file. The value of the
+symbol is the start address of portion of the text section corresponding
+to that file.
+
+With the Sun Solaris2 compiler, the @code{desc} field contains a
+source-language code.
+
+Some compilers (for example, gcc2 and SunOS4 @file{/bin/cc}) also
+include the directory in which the source was compiled, in a second
+@code{N_SO} symbol preceding the one containing the file name. This
+symbol can be distinguished by the fact that it ends in a slash. Code
+from the cfront C++ compiler can have additional @code{N_SO} symbols for
+nonexistent source files after the @code{N_SO} for the real source file;
+these are believed to contain no useful information.
+
+For example:
+
+@example
+.stabs "/cygint/s1/users/jcm/play/",100,0,0,Ltext0 ; 100 is N_SO
+.stabs "hello.c",100,0,0,Ltext0
+ .text
+Ltext0:
+@end example
+
+Instead of @code{N_SO} symbols, XCOFF uses a @code{.file} assembler
+directive which assembles to a standard COFF @code{.file} symbol;
+explaining this in detail is outside the scope of this document.
+
+There are several different schemes for dealing with include files: the
+traditional @code{N_SOL} approach, Sun's @code{N_BINCL} scheme, and the
+XCOFF @code{C_BINCL} (which despite the similar name has little in
+common with @code{N_BINCL}).
+
+An @code{N_SOL} symbol specifies which include file subsequent symbols
+refer to. The string field is the name of the file and the value is the
+text address corresponding to the start of the previous include file and
+the start of this one. To specify the main source file again, use an
+@code{N_SOL} symbol with the name of the main source file.
+
+A @code{N_BINCL} symbol specifies the start of an include file. In an
+object file, only the name is significant. The Sun linker puts data
+into some of the other fields. The end of the include file is marked by
+a @code{N_EINCL} symbol (which has no name field). In an ojbect file,
+there is no significant data in the @code{N_EINCL} symbol; the Sun
+linker puts data into some of the fields. @code{N_BINCL} and
+@code{N_EINCL} can be nested. If the linker detects that two source
+files have identical stabs with a @code{N_BINCL} and @code{N_EINCL} pair
+(as will generally be the case for a header file), then it only puts out
+the stabs once. Each additional occurance is replaced by an
+@code{N_EXCL} symbol. I believe the Sun (SunOS4, not sure about
+Solaris) linker is the only one which supports this feature.
+
+For the start of an include file in XCOFF, use the @file{.bi} assembler
+directive which generates a @code{C_BINCL} symbol. A @file{.ei}
+directive, which generates a @code{C_EINCL} symbol, denotes the end of
+the include file. Both directives are followed by the name of the
+source file in quotes, which becomes the string for the symbol. The
+value of each symbol, produced automatically by the assembler and
+linker, is an offset into the executable which points to the beginning
+(inclusive, as you'd expect) and end (inclusive, as you would not
+expect) of the portion of the COFF linetable which corresponds to this
+include file. @code{C_BINCL} and @code{C_EINCL} do not nest.
+
+@node Line Numbers
@section Line Numbers
-@table @strong
-@item Directive:
-@code{.stabn}
-@item Type:
-@code{N_SLINE}
-@end table
-
-The start of source lines is represented by the @code{N_SLINE} (68) stab
-type.
+A @code{N_SLINE} symbol represents the start of a source line. The
+@var{desc} field contains the line number and the @var{value} field
+contains the code address for the start of that source line. On most
+machines the address is absolute; for Sun's stabs-in-elf, it is relative
+to the function in which the @code{N_SLINE} symbol occurs.
+
+GNU documents @code{N_DSLINE} and @code{N_BSLINE} symbols for line
+numbers in the data or bss segments, respectively. They are identical
+to @code{N_SLINE} but are relocated differently by the linker. They
+were intended to be used to describe the source location of a variable
+declaration, but I believe that gcc2 actually puts the line number in
+the desc field of the stab for the variable itself. GDB has been
+ignoring these symbols (unless they contain a string field) at least
+since GDB 3.5.
+
+XCOFF uses COFF line numbers instead, which are outside the scope of
+this document, ammeliorated by adequate marking of include files
+(@pxref{Source Files}).
-@example
-.stabn N_SLINE, NIL, @var{line}, @var{address}
-@end example
-
-@var{line} is a source line number; @var{address} represents the code
-address for the start of that source line.
-
-@example
-27 _main:
-28 .stabn 68,0,4,LM1
-29 LM1:
-30 !#PROLOGUE# 0
-@end example
+For single source lines that generate discontiguous code, such as flow
+of control statements, there may be more than one line number entry for
+the same source line. In this case there is a line number entry at the
+start of each code range, each with the same line number.
@node Procedures
-@section Procedures
-
-@table @strong
-@item Directive:
-@code{.stabs}
-@item Type:
-@code{N_FUN}
-@item Symbol Descriptors:
-@code{f} (local), @code{F} (global)
-@end table
-
-Procedures are described by the @code{N_FUN} stab type. The symbol
-descriptor for a procedure is @samp{F} if the procedure is globally
-scoped and @samp{f} if the procedure is static (locally scoped).
-
-The @code{N_FUN} stab representing a procedure is located immediately
-following the code of the procedure. The @code{N_FUN} stab is in turn
-directly followed by a group of other stabs describing elements of the
-procedure. These other stabs describe the procedure's parameters, its
-block local variables and its block structure.
+@section Procedures
+
+All of the following stabs use the @samp{N_FUN} symbol type.
+
+A function is represented by a @samp{F} symbol descriptor for a global
+(extern) function, and @samp{f} for a static (local) function. The next
+@samp{N_SLINE} symbol can be used to find the line number of the start
+of the function. The value field is the address of the start of the
+function. The type information of the stab represents the return type
+of the function; thus @samp{foo:f5} means that foo is a function
+returning type 5.
+
+The type information of the stab is optionally followed by type
+information for each argument, with each argument preceded by @samp{;}.
+An argument type of 0 means that additional arguments are being passed,
+whose types and number may vary (@samp{...} in ANSI C). This extension
+is used by Sun's Solaris compiler. GDB has tolerated it (i.e. at least
+parsed the syntax, if not necessarily used the information) at least
+since version 4.8; I don't know whether all versions of dbx will
+tolerate it. The argument types given here are not merely redundant
+with the symbols for the arguments themselves (@pxref{Parameters}), they
+are the types of the arguments as they are passed, before any
+conversions might take place. For example, if a C function which is
+declared without a prototype takes a @code{float} argument, the value is
+passed as a @code{double} but then converted to a @code{float}.
+Debuggers need to use the types given in the arguments when printing
+values, but if calling the function they need to use the types given in
+the symbol defining the function.
+
+If the return type and types of arguments of a function which is defined
+in another source file are specified (i.e. a function prototype in ANSI
+C), traditionally compilers emit no stab; the only way for the debugger
+to find the information is if the source file where the function is
+defined was also compiled with debugging symbols. As an extension the
+Solaris compiler uses symbol descriptor @samp{P} followed by the return
+type of the function, followed by the arguments, each preceded by
+@samp{;}, as in a stab with symbol descriptor @samp{f} or @samp{F}.
+This use of symbol descriptor @samp{P} can be distinguished from its use
+for register parameters (@pxref{Parameters}) by the fact that it has
+symbol type @code{N_FUN}.
+
+The AIX documentation also defines symbol descriptor @samp{J} as an
+internal function. I assume this means a function nested within another
+function. It also says Symbol descriptor @samp{m} is a module in
+Modula-2 or extended Pascal.
+
+Procedures (functions which do not return values) are represented as
+functions returning the void type in C. I don't see why this couldn't
+be used for all languages (inventing a void type for this purpose if
+necessary), but the AIX documentation defines @samp{I}, @samp{P}, and
+@samp{Q} for internal, global, and static procedures, respectively.
+These symbol descriptors are unusual in that they are not followed by
+type information.
+
+For any of the above symbol descriptors, after the symbol descriptor and
+the type information, there is optionally a comma, followed by the name
+of the procedure, followed by a comma, followed by a name specifying the
+scope. The first name is local to the scope specified. I assume then
+that the name of the symbol (before the @samp{:}), if specified, is some
+sort of global name. I assume the name specifying the scope is the name
+of a function specifying that scope. This feature is an AIX extension,
+and this information is based on the manual; I haven't actually tried
+it.
+
+The stab representing a procedure is located immediately following the
+code of the procedure. This stab is in turn directly followed by a
+group of other stabs describing elements of the procedure. These other
+stabs describe the procedure's parameters, its block local variables and
+its block structure.
@example
48 ret
@node Block Structure
@section Block Structure
-@table @strong
-@item Directive:
-@code{.stabn}
-@item Types:
-@code{N_LBRAC}, @code{N_RBRAC}
-@end table
-
The program's block structure is represented by the @code{N_LBRAC} (left
-brace) and the @code{N_RBRAC} (right brace) stab types. The following code
-range, which is the body of @code{main}, is labeled with @samp{LBB2:} at the
-beginning and @samp{LBE2:} at the end.
-
-@example
-37 LBB2:
-38 sethi %hi(LC0),%o1
-39 or %o1,%lo(LC0),%o0
-40 call _printf,0
-41 nop
-42 .stabn 68,0,6,LM3
-43 LM3:
-44 LBE2:
-@end example
+brace) and the @code{N_RBRAC} (right brace) stab types. The variables
+defined inside a block preceded the @code{N_LBRAC} symbol for most
+compilers, including GCC. Other compilers, such as the Convex, Acorn
+RISC machine, and Sun acc compilers, put the variables after the
+@code{N_LBRAC} symbol. The values of the @code{N_LBRAC} and
+@code{N_RBRAC} symbols are the start and end addresses of the code of
+the block, respectively. For most machines, they are relative to the
+starting address of this source file. For the Gould NP1, they are
+absolute. For Sun's stabs-in-elf, they are relative to the function in
+which they occur.
The @code{N_LBRAC} and @code{N_RBRAC} stabs that describe the block
-scope of the procedure are located after the @code{N_FUNC} stab that
-represents the procedure itself. The @code{N_LBRAC} uses the
-@code{LBB2} label as the code address in its value field, and the
-@code{N_RBRAC} uses @code{LBE2}.
-
-@example
-50 .stabs "main:F1",36,0,0,_main
-@end example
-
-@example
- .stabn N_LBRAC, NIL, NIL, @var{left-brace-address}
- .stabn N_RBRAC, NIL, NIL, @var{right-brace-address}
-@end example
-
-@example
-51 .stabn 192,0,0,LBB2
-52 .stabn 224,0,0,LBE2
-@end example
-
-@node Simple types
-@chapter Simple types
-
-@menu
-* Basic types:: Basic type definitions
-* Range types:: Range types defined by min and max value
-* Float "range" types:: Range type defined by size in bytes
-@end menu
-
-@node Basic types
-@section Basic type definitions
-
-@table @strong
-@item Directive:
-@code{.stabs}
-@item Type:
-@code{N_LSYM}
-@item Symbol Descriptor:
-@code{t}
-@end table
-
-The basic types for the language are described using the @code{N_LSYM} stab
-type. They are boilerplate and are emited by the compiler for each
-compilation unit. Basic type definitions are not always a complete
-description of the type and are sometimes circular. The debugger
-recognizes the type anyway, and knows how to read bits as that type.
-
-Each language and compiler defines a slightly different set of basic
-types. In this example we are looking at the basic types for C emited
-by the GNU compiler targeting the Sun4. Here the basic types are
-mostly defined as range types.
-
-
-@node Range types
-@section Range types defined by min and max value
+scope of a procedure are located after the @code{N_FUN} stab that
+represents the procedure itself.
-@table @strong
-@item Type Descriptor:
-@code{r}
-@end table
-
-When defining a range type, if the number after the first semicolon is
-smaller than the number after the second one, then the two numbers
-represent the smallest and the largest values in the range.
-
-@example
-4 .text
-5 Ltext0:
-
-.stabs "@var{name}:
- @var{descriptor} @r{(type)}
- @var{type-def}=
- @var{type-desc}
- @var{type-ref};
- @var{low-bound};
- @var{high-bound};
- ",
- N_LSYM, NIL, NIL, NIL
-
-6 .stabs "int:t1=r1;-2147483648;2147483647;",128,0,0,0
-7 .stabs "char:t2=r2;0;127;",128,0,0,0
-@end example
-
-Here the integer type (@code{1}) is defined as a range of the integer
-type (@code{1}). Likewise @code{char} is a range of @code{char}. This
-part of the definition is circular, but at least the high and low bound
-values of the range hold more information about the type.
-
-Here short unsigned int is defined as type number 8 and described as a
-range of type @code{int}, with a minimum value of 0 and a maximum of 65535.
+Sun documents the @code{desc} field of @code{N_LBRAC} and
+@code{N_RBRAC} symbols as containing the nesting level of the block.
+However, dbx seems not to care, and GCC just always set @code{desc} to
+zero.
-@example
-13 .stabs "short unsigned int:t8=r1;0;65535;",128,0,0,0
-@end example
+@node Constants
+@chapter Constants
-@node Float "range" types
-@section Range type defined by size in bytes
+The @samp{c} symbol descriptor indicates that this stab represents a
+constant. This symbol descriptor is an exception to the general rule
+that symbol descriptors are followed by type information. Instead, it
+is followed by @samp{=} and one of the following:
-@table @strong
-@item Type Descriptor:
-@code{r}
+@table @code
+@item b @var{value}
+Boolean constant. @var{value} is a numeric value; I assume it is 0 for
+false or 1 for true.
+
+@item c @var{value}
+Character constant. @var{value} is the numeric value of the constant.
+
+@item e @var{type-information} , @var{value}
+Constant whose value can be represented as integral.
+@var{type-information} is the type of the constant, as it would appear
+after a symbol descriptor (@pxref{Stabs Format}). @var{value} is the
+numeric value of the constant. GDB 4.9 does not actually get the right
+value if @var{value} does not fit in a host @code{int}, but it does not
+do anything violent, and future debuggers could be extended to accept
+integers of any size (whether unsigned or not). This constant type is
+usually documented as being only for enumeration constants, but GDB has
+never imposed that restriction; I don't know about other debuggers.
+
+@item i @var{value}
+Integer constant. @var{value} is the numeric value. The type is some
+sort of generic integer type (for GDB, a host @code{int}); to specify
+the type explicitly, use @samp{e} instead.
+
+@item r @var{value}
+Real constant. @var{value} is the real value, which can be @samp{INF}
+(optionally preceded by a sign) for infinity, @samp{QNAN} for a quiet
+NaN (not-a-number), or @samp{SNAN} for a signalling NaN. If it is a
+normal number the format is that accepted by the C library function
+@code{atof}.
+
+@item s @var{string}
+String constant. @var{string} is a string enclosed in either @samp{'}
+(in which case @samp{'} characters within the string are represented as
+@samp{\'} or @samp{"} (in which case @samp{"} characters within the
+string are represented as @samp{\"}).
+
+@item S @var{type-information} , @var{elements} , @var{bits} , @var{pattern}
+Set constant. @var{type-information} is the type of the constant, as it
+would appear after a symbol descriptor (@pxref{Stabs Format}).
+@var{elements} is the number of elements in the set (Does this means
+how many bits of @var{pattern} are actually used, which would be
+redundant with the type, or perhaps the number of bits set in
+@var{pattern}? I don't get it), @var{bits} is the number of bits in the
+constant (meaning it specifies the length of @var{pattern}, I think),
+and @var{pattern} is a hexadecimal representation of the set. AIX
+documentation refers to a limit of 32 bytes, but I see no reason why
+this limit should exist. This form could probably be used for arbitrary
+constants, not just sets; the only catch is that @var{pattern} should be
+understood to be target, not host, byte order and format.
@end table
-In a range definition, if the first number after the semicolon is
-positive and the second is zero, then the type being defined is a
-floating point type, and the number after the first semicolon is the
-number of bytes needed to represent the type. Note that this does not
-provide a way to distinguish 8-byte real floating point types from
-8-byte complex floating point types.
-
-@example
-.stabs "@var{name}:
- @var{desc}
- @var{type-def}=
- @var{type-desc}
- @var{type-ref};
- @var{bit-count};
- 0;
- ",
- N_LSYM, NIL, NIL, NIL
-
-17 .stabs "float:t12=r1;4;0;",128,0,0,0
-18 .stabs "double:t13=r1;8;0;",128,0,0,0
-19 .stabs "long double:t14=r1;8;0;",128,0,0,0
-@end example
-
-Cosmically enough, the @code{void} type is defined directly in terms of
-itself.
-
-@example
-.stabs "@var{name}:
- @var{symbol-desc}
- @var{type-def}=
- @var{type-ref}
- ",N_LSYM,NIL,NIL,NIL
-
-20 .stabs "void:t15=15",128,0,0,0
-@end example
+The boolean, character, string, and set constants are not supported by
+GDB 4.9, but it will ignore them. GDB 4.8 and earlier gave an error
+message and refused to read symbols from the file containing the
+constants.
+This information is followed by @samp{;}.
@node Example
@chapter A Comprehensive Example in C
@chapter Variables
@menu
-* Automatic variables:: locally scoped
-* Global variables::
-* Register variables::
-* Initialized statics::
-* Un-initialized statics::
-* Parameters::
+* Automatic variables:: Variables allocated on the stack.
+* Global Variables:: Variables used by more than one source file.
+* Register variables:: Variables in registers.
+* Common Blocks:: Variables statically allocated together.
+* Statics:: Variables local to one source file.
+* Parameters:: Variables for arguments to functions.
@end menu
@node Automatic variables
none
@end table
-
In addition to describing types, the @code{N_LSYM} stab type also
describes locally scoped automatic variables. Refer again to the body
of @code{main} in @file{example2.c}. It allocates two automatic
@exdent @code{N_LSYM} (128): automatic variable, scoped locally to @code{main}
.stabs "@var{name}:
- @var{type-ref}",
+ @var{type information}",
N_LSYM, NIL, NIL,
@var{frame-pointer-offset}
@exdent @code{N_LSYM} (128): automatic variable, scoped locally to the @code{for} loop
.stabs "@var{name}:
- @var{type-ref}",
+ @var{type information}",
N_LSYM, NIL, NIL,
@var{frame-pointer-offset}
101 .stabn 192,0,0,LBB3 ## begin `for' loop N_LBRAC
@end example
-Since the character in the string field following the colon is not a
-letter, there is no symbol descriptor. This means that the stab
-describes a local variable, and that the number after the colon is a
-type reference. In this case it a a reference to the basic type @code{int}.
-Notice also that the frame pointer offset is negative number for
-automatic variables.
-
+The symbol descriptor is omitted for automatic variables. Since type
+information should being with a digit, @samp{-}, or @samp{(}, only
+digits, @samp{-}, and @samp{(} are precluded from being used for symbol
+descriptors by this fact. However, the Acorn RISC machine (ARM) is said
+to get this wrong: it puts out a mere type definition here, without the
+preceding @code{@var{typenumber}=}. This is a bad idea; there is no
+guarantee that type descriptors are distinct from symbol descriptors.
@node Global Variables
@section Global Variables
external symbol for the global variable.
@node Register variables
-@section Global register variables
+@section Register variables
-@table @strong
-@item Directive:
-@code{.stabs}
-@item Type:
-@code{N_RSYM}
-@item Symbol Descriptor:
-@code{r}
-@end table
+@c According to an old version of this manual, AIX uses C_RPSYM instead
+@c of C_RSYM. I am skeptical; this should be verified.
+Register variables have their own stab type, @code{N_RSYM}, and their
+own symbol descriptor, @code{r}. The stab's value field contains the
+number of the register where the variable data will be stored.
-The following source line defines a global variable, @code{g_bar}, which is
-explicitly allocated in global register @code{%g5}.
+The value is the register number.
-@example
-2 register int g_bar asm ("%g5");
-@end example
+AIX defines a separate symbol descriptor @samp{d} for floating point
+registers. This seems unnecessary---why not just just give floating
+point registers different register numbers? I have not verified whether
+the compiler actually uses @samp{d}.
-Register variables have their own stab type, @code{N_RSYM}, and their own
-symbol descriptor, @code{r}. The stab's value field contains the number of
-the register where the variable data will be stored. Since the
-variable was not initialized in this compilation unit, the stab is
-emited at the end of the object file, with the stabs for other
-uninitialized globals (@code{bcc}).
+If the register is explicitly allocated to a global variable, but not
+initialized, as in
@example
-@exdent @code{N_RSYM} (64): register variable
-
-.stabs "@var{name}:
- @var{descriptor}
- @var{type-ref}",
- N_RSYM, NIL, NIL,
- @var{register}
-
-133 .stabs "g_bar:r1",64,0,0,5
+register int g_bar asm ("%g5");
@end example
+the stab may be emitted at the end of the object file, with
+the other bss symbols.
-@node Initialized statics
-@section Initialized static variables
-
-@table @strong
-@item Directive:
-@code{.stabs}
-@item Type:
-@code{N_STSYM}
-@item Symbol Descriptors:
-@code{S} (file scope), @code{V} (procedure scope)
-@end table
-
-Initialized static variables are represented by the @code{N_STSYM} stab
-type. The symbol descriptor part of the string field shows if the
-variable is file scope static (@samp{S}) or procedure scope static
-(@samp{V}). The source line
-
-@example
-3 static int s_g_repeat = 2;
-@end example
-
-@noindent
-yields the following code. The stab is located immediately preceding
-the storage for the variable it represents. Since the variable in
-this example is file scope static the symbol descriptor is @samp{S}.
+@node Common Blocks
+@section Common Blocks
-@example
-@exdent @code{N_STSYM} (38): initialized static variable (data seg w/internal linkage)
+A common block is a statically allocated section of memory which can be
+referred to by several source files. It may contain several variables.
+I believe @sc{fortran} is the only language with this feature. A
+@code{N_BCOMM} stab begins a common block and an @code{N_ECOMM} stab
+ends it. The only thing which is significant about these two stabs is
+their name, which can be used to look up a normal (non-debugging) symbol
+which gives the address of the common block. Then each stab between the
+@code{N_BCOMM} and the @code{N_ECOMM} specifies a member of that common
+block; its value is the offset within the common block of that variable.
+The @code{N_ECOML} stab type is documented for this purpose, but Sun's
+@sc{fortran} compiler uses @code{N_GSYM} instead. The test case I
+looked at had a common block local to a function and it used the
+@samp{V} symbol descriptor; I assume one would use @samp{S} if not local
+to a function (that is, if a common block @emph{can} be anything other
+than local to a function).
-.stabs "@var{name}:
- @var{descriptor}
- @var{type-ref}",
- N_STSYM,NIL,NIL,
- @var{address}
-
-26 .stabs "s_g_repeat:S1",38,0,0,_s_g_repeat
-27 .align 4
-28 _s_g_repeat:
-29 .word 2
-@end example
+@node Statics
+@section Static Variables
+Initialized static variables are represented by the @samp{S} and
+@samp{V} symbol descriptors. @samp{S} means file scope static, and
+@samp{V} means procedure scope static.
-@node Un-initialized statics
-@section Un-initialized static variables
+In a.out files, @code{N_STSYM} means the data segment (although gcc
+2.4.5 has a bug in that it uses @code{N_FUN}, so neither dbx nor gdb can
+find the variables), @code{N_FUN} means the text segment, and
+@code{N_LCSYM} means the bss segment.
-@table @strong
-@item Directive:
-@code{.stabs}
-@item Type:
-@code{N_LCSYM}
-@item Symbol Descriptors:
-@code{S} (file scope), @code{V} (procedure scope)
-@end table
+In xcoff files, each symbol has a section number, so the symbol type
+need not indicate the segment.
-Un-initialized static variables are represented by the @code{N_LCSYM}
-stab type. The symbol descriptor part of the string shows if the
-variable is file scope static (@samp{S}) or procedure scope static
-(@samp{V}). In this example it is procedure scope static. The source
-line allocating @code{s_flap} immediately follows the open brace for the
-procedure @code{main}.
+@c In ELF files, it apparently is a big mess. See kludge in dbxread.c
+@c in GDB. FIXME: Investigate where this kludge comes from.
+@c
+@c This is the place to mention N_ROSYM; I'd rather do so once I can
+@c coherently explain how this stuff works for stabs-in-elf.
+@c
+For example, the source lines
@example
-20 @{
-21 static float s_flap;
+static const int var_const = 5;
+static int var_init = 2;
+static int var_noinit;
@end example
-The code that reserves storage for the variable @code{s_flap} precedes the
-body of body of @code{main}.
+@noindent
+yield the following stabs:
@example
-39 .reserve _s_flap.0,4,"bss",4
+.stabs "var_const:S1",36,0,0,_var_const ; @r{36 = N_FUN}
+. . .
+.stabs "var_init:S1",38,0,0,_var_init ; @r{38 = N_STSYM}
+. . .
+.stabs "var_noinit:S1",40,0,0,_var_noinit ; @r{40 = N_LCSYM}
@end example
-But since @code{s_flap} is scoped locally to @code{main}, its stab is
-located with the other stabs representing symbols local to @code{main}.
-The stab for @code{s_flap} is located just before the @code{N_LBRAC} for
-@code{main}.
+@node Parameters
+@section Parameters
+
+Parameters to a function are represented by a stab (or sometimes two,
+see below) for each parameter. The stabs are in the order in which the
+debugger should print the parameters (i.e. the order in which the
+parameters are declared in the source file).
+
+The symbol descriptor @samp{p} is used to refer to parameters which are
+in the arglist. Symbols have symbol type @samp{N_PSYM}. The value of
+the symbol is the offset relative to the argument list.
+
+If the parameter is passed in a register, then the traditional way to do
+this is to provide two symbols for each argument:
+
+@example
+.stabs "arg:p1" . . . ; N_PSYM
+.stabs "arg:r1" . . . ; N_RSYM
+@end example
+
+Debuggers are expected to use the second one to find the value, and the
+first one to know that it is an argument.
+
+Because this is kind of ugly, some compilers use symbol descriptor
+@samp{P} or @samp{R} to indicate an argument which is in a register.
+The symbol value is the register number. @samp{P} and @samp{R} mean the
+same thing, the difference is that @samp{P} is a GNU invention and
+@samp{R} is an IBM (xcoff) invention. As of version 4.9, GDB should
+handle either one. Symbol type @samp{C_RPSYM} is used with @samp{R} and
+@samp{N_RSYM} is used with @samp{P}.
+
+According to the AIX documentation symbol descriptor @samp{D} is for a
+parameter passed in a floating point register. This seems
+unnecessary---why not just use @samp{R} with a register number which
+indicates that it's a floating point register? I haven't verified
+whether the system actually does what the documentation indicates.
+
+There is at least one case where GCC uses a @samp{p}/@samp{r} pair
+rather than @samp{P}; this is where the argument is passed in the
+argument list and then loaded into a register.
+
+On the sparc and hppa, for a @samp{P} symbol whose type is a structure
+or union, the register contains the address of the structure. On the
+sparc, this is also true of a @samp{p}/@samp{r} pair (using Sun cc) or a
+@samp{p} symbol. However, if a (small) structure is really in a
+register, @samp{r} is used. And, to top it all off, on the hppa it
+might be a structure which was passed on the stack and loaded into a
+register and for which there is a @samp{p}/@samp{r} pair! I believe
+that symbol descriptor @samp{i} is supposed to deal with this case, (it
+is said to mean "value parameter by reference, indirect access", I don't
+know the source for this information) but I don't know details or what
+compilers or debuggers use it, if any (not GDB or GCC). It is not clear
+to me whether this case needs to be dealt with differently than
+parameters passed by reference (see below).
+
+There is another case similar to an argument in a register, which is an
+argument which is actually stored as a local variable. Sometimes this
+happens when the argument was passed in a register and then the compiler
+stores it as a local variable. If possible, the compiler should claim
+that it's in a register, but this isn't always done. Some compilers use
+the pair of symbols approach described above ("arg:p" followed by
+"arg:"); this includes gcc1 (not gcc2) on the sparc when passing a small
+structure and gcc2 (sometimes) when the argument type is float and it is
+passed as a double and converted to float by the prologue (in the latter
+case the type of the "arg:p" symbol is double and the type of the "arg:"
+symbol is float). GCC, at least on the 960, uses a single @samp{p}
+symbol descriptor for an argument which is stored as a local variable
+but uses @samp{N_LSYM} instead of @samp{N_PSYM}. In this case the value
+of the symbol is an offset relative to the local variables for that
+function, not relative to the arguments (on some machines those are the
+same thing, but not on all).
+
+If the parameter is passed by reference (e.g. Pascal VAR parameters),
+then type symbol descriptor is @samp{v} if it is in the argument list,
+or @samp{a} if it in a register. Other than the fact that these contain
+the address of the parameter other than the parameter itself, they are
+identical to @samp{p} and @samp{R}, respectively. I believe @samp{a} is
+an AIX invention; @samp{v} is supported by all stabs-using systems as
+far as I know.
+
+@c Is this paragraph correct? It is based on piecing together patchy
+@c information and some guesswork
+Conformant arrays refer to a feature of Modula-2, and perhaps other
+languages, in which the size of an array parameter is not known to the
+called function until run-time. Such parameters have two stabs, a
+@samp{x} for the array itself, and a @samp{C}, which represents the size
+of the array. The value of the @samp{x} stab is the offset in the
+argument list where the address of the array is stored (it this right?
+it is a guess); the value of the @samp{C} stab is the offset in the
+argument list where the size of the array (in elements? in bytes?) is
+stored.
+
+The following are also said to go with @samp{N_PSYM}:
@example
-@exdent @code{N_LCSYM} (40): uninitialized static var (BSS seg w/internal linkage)
-
-.stabs "@var{name}:
- @var{descriptor}
- @var{type-ref}",
- N_LCSYM, NIL, NIL,
- @var{address}
+"name" -> "param_name:#type"
+ -> pP (<<??>>)
+ -> pF FORTRAN function parameter
+ -> X (function result variable)
+ -> b (based variable)
-97 .stabs "s_flap:V12",40,0,0,_s_flap.0
-98 .stabs "times:1",128,0,0,-20
-99 .stabn 192,0,0,LBB2 # N_LBRAC for main.
+value -> offset from the argument pointer (positive).
@end example
-@c ............................................................
-
-@node Parameters
-@section Parameters
-
-@table @strong
-@item Directive:
-@code{.stabs}
-@item Type:
-@code{N_PSYM}
-@item Symbol Descriptor:
-@code{p}
-@end table
-
-Procedure parameters are represented by the N_PSYM stab type. The
-following source lines show the parameters of the main routine.
+As a simple example, the code
@example
-17 main (argc, argv)
-18 int argc;
-19 char* argv[];
-20 @{
+main (argc, argv)
+ int argc;
+ char **argv;
+@{
@end example
-The N_PSYM stabs describing parameters to a function directly follow
-the N_FUN stab that represents the procedure itself. The N_FUN stab
-immediately follows the code of the procedure it describes. Following
-the N_PSYM parameter stabs are any N_LSYM stabs representing local
-variables.
+produces the stabs
@example
-@exdent <36> N_FUN - describing the procedure main
-
-94 .stabs "main:F1",36,0,0,_main
-
-@exdent <160> N_PSYM - parameters
-@exdent .stabs "name:sym_desc(value_param)type_ref(int)", N_PSYM,
-@exdent NIL, NIL, frame_ptr_offset
-
-95 .stabs "argc:p1",160,0,0,68
-
-@exdent <160> N_PSYM - parameter
-@exdent .stabs "name:sym_desc(value_param)type_def(20)=ptr_to type_def(21)=
-@exdent ptr_to type_ref(char)
-
-96 .stabs "argv:p20=*21=*2",160,0,0,72
+.stabs "main:F1",36,0,0,_main ; 36 is N_FUN
+.stabs "argc:p1",160,0,0,68 ; 160 is N_PSYM
+.stabs "argv:p20=*21=*2",160,0,0,72
@end example
-The type definition of argv is interesting because it defines two new
-types in terms of an existing one. The array argv contains character
-pointers. The type of the array name is a pointer to the type the
-array holds. Thus the type of argv is ptr to ptr to char. The stab
-for argv contains nested type_definitions. Type 21 is ptr to type 2
-(char) and argv (type 20) is ptr to type 21.
+The type definition of argv is interesting because it contains several
+type definitions. Type 21 is pointer to type 2 (char) and argv (type 20) is
+pointer to type 21.
-@node Aggregate Types
-@chapter Aggregate Types
+@node Types
+@chapter Type Definitions
Now let's look at some variable definitions involving complex types.
This involves understanding better how types are described. In the
type definition.
@menu
-* Arrays::
-* Enumerations::
-* Structure tags::
-* Typedefs::
-* Unions::
-* Function types::
+* Builtin types:: Integers, floating point, void, etc.
+* Miscellaneous Types:: Pointers, sets, files, etc.
+* Cross-references:: Referring to a type not yet defined.
+* Subranges:: A type with a specific range.
+* Arrays:: An aggregate type of same-typed elements.
+* Strings:: Like an array but also has a length.
+* Enumerations:: Like an integer but the values have names.
+* Structures:: An aggregate type of different-typed elements.
+* Typedefs:: Giving a type a name.
+* Unions:: Different types sharing storage.
+* Function Types::
@end menu
-@node Arrays
-@section Array types
+@node Builtin types
+@section Builtin types
-@table @strong
-@item Directive:
-@code{.stabs}
-@item Types:
-@code{N_GSYM}, @code{N_LSYM}
-@item Symbol Descriptor:
-@code{T}
-@item Type Descriptor:
-@code{ar}
-@end table
+Certain types are built in (@code{int}, @code{short}, @code{void},
+@code{float}, etc.); the debugger recognizes these types and knows how
+to handle them. Thus don't be surprised if some of the following ways
+of specifying builtin types do not specify everything that a debugger
+would need to know about the type---in some cases they merely specify
+enough information to distinguish the type from other types.
+
+The traditional way to define builtin types is convolunted, so new ways
+have been invented to describe them. Sun's ACC uses the @samp{b} and
+@samp{R} type descriptors, and IBM uses negative type numbers. GDB can
+accept all three, as of version 4.8; dbx just accepts the traditional
+builtin types and perhaps one of the other two formats.
+
+@menu
+* Traditional Builtin Types:: Put on your seatbelts and prepare for kludgery
+* Builtin Type Descriptors:: Builtin types with special type descriptors
+* Negative Type Numbers:: Builtin types using negative type numbers
+@end menu
+
+@node Traditional Builtin Types
+@subsection Traditional Builtin types
-As an example of an array type consider the global variable below.
+Often types are defined as subranges of themselves. If the array bounds
+can fit within an @code{int}, then they are given normally. For example:
@example
-15 char char_vec[3] = @{'a','b','c'@};
+.stabs "int:t1=r1;-2147483648;2147483647;",128,0,0,0 ; 128 is N_LSYM
+.stabs "char:t2=r2;0;127;",128,0,0,0
@end example
-Since the array is a global variable, it is described by the N_GSYM
-stab type. The symbol descriptor G, following the colon in stab's
-string field, also says the array is a global variable. Following the
-G is a definition for type (19) as shown by the equals sign after the
-type number.
+Builtin types can also be described as subranges of @code{int}:
-After the equals sign is a type descriptor, ar, which says that the
-type being defined is an array. Following the type descriptor for an
-array is the type of the index, a null field, the upper bound of the
-array indexing, and the type of the array elements.
+@example
+.stabs "unsigned short:t6=r1;0;65535;",128,0,0,0
+@end example
-The array definition above generates the assembly language that
-follows.
+If the lower bound of a subrange is 0 and the upper bound is -1, it
+means that the type is an unsigned integral type whose bounds are too
+big to describe in an int. Traditionally this is only used for
+@code{unsigned int} and @code{unsigned long}; GCC also sometimes uses it
+for @code{long long} and @code{unsigned long long}, and the only way to
+tell those types apart is to look at their names. On other machines GCC
+puts out bounds in octal, with a leading 0. In this case a negative
+bound consists of a number which is a 1 bit followed by a bunch of 0
+bits, and a positive bound is one in which a bunch of bits are 1.
@example
-@exdent <32> N_GSYM - global variable
-@exdent .stabs "name:sym_desc(global)type_def(19)=type_desc(array)
-@exdent index_type_ref(int);NIL;high_bound(2);element_type_ref(char)";
-@exdent N_GSYM, NIL, NIL, NIL
-
-32 .stabs "char_vec:G19=ar1;0;2;2",32,0,0,0
-33 .global _char_vec
-34 .align 4
-35 _char_vec:
-36 .byte 97
-37 .byte 98
-38 .byte 99
+.stabs "unsigned int:t4=r1;0;-1;",128,0,0,0
+.stabs "long long int:t7=r1;0;-1;",128,0,0,0
@end example
-@node Enumerations
-@section Enumerations
+If the lower bound of a subrange is 0 and the upper bound is negative,
+it means that it is an unsigned integral type whose size in bytes is the
+absolute value of the upper bound. I believe this is a Convex
+convention for @code{unsigned long long}.
-@table @strong
-@item Directive:
-@code{.stabs}
-@item Type:
-@code{N_LSYM}
-@item Symbol Descriptor:
-@code{T}
-@item Type Descriptor:
-@code{e}
-@end table
+If the lower bound of a subrange is negative and the upper bound is 0,
+it means that the type is a signed integral type whose size in bytes is
+the absolute value of the lower bound. I believe this is a Convex
+convention for @code{long long}. To distinguish this from a legitimate
+subrange, the type should be a subrange of itself. I'm not sure whether
+this is the case for Convex.
+If the upper bound of a subrange is 0, it means that this is a floating
+point type, and the lower bound of the subrange indicates the number of
+bytes in the type:
+
+@example
+.stabs "float:t12=r1;4;0;",128,0,0,0
+.stabs "double:t13=r1;8;0;",128,0,0,0
+@end example
+
+However, GCC writes @code{long double} the same way it writes
+@code{double}; the only way to distinguish them is by the name:
+
+@example
+.stabs "long double:t14=r1;8;0;",128,0,0,0
+@end example
+
+Complex types are defined the same way as floating-point types; the only
+way to distinguish a single-precision complex from a double-precision
+floating-point type is by the name.
+
+The C @code{void} type is defined as itself:
+
+@example
+.stabs "void:t15=15",128,0,0,0
+@end example
+
+I'm not sure how a boolean type is represented.
+
+@node Builtin Type Descriptors
+@subsection Defining Builtin Types using Builtin Type Descriptors
+
+There are various type descriptors to define builtin types:
+
+@table @code
+@c FIXME: clean up description of width and offset, once we figure out
+@c what they mean
+@item b @var{signed} @var{char-flag} @var{width} ; @var{offset} ; @var{nbits} ;
+Define an integral type. @var{signed} is @samp{u} for unsigned or
+@samp{s} for signed. @var{char-flag} is @samp{c} which indicates this
+is a character type, or is omitted. I assume this is to distinguish an
+integral type from a character type of the same size, for example it
+might make sense to set it for the C type @code{wchar_t} so the debugger
+can print such variables differently (Solaris does not do this). Sun
+sets it on the C types @code{signed char} and @code{unsigned char} which
+arguably is wrong. @var{width} and @var{offset} appear to be for small
+objects stored in larger ones, for example a @code{short} in an
+@code{int} register. @var{width} is normally the number of bytes in the
+type. @var{offset} seems to always be zero. @var{nbits} is the number
+of bits in the type.
+
+Note that type descriptor @samp{b} used for builtin types conflicts with
+its use for Pascal space types (@pxref{Miscellaneous Types}); they can
+be distinguished because the character following the type descriptor
+will be a digit, @samp{(}, or @samp{-} for a Pascal space type, or
+@samp{u} or @samp{s} for a builtin type.
+
+@item w
+Documented by AIX to define a wide character type, but their compiler
+actually uses negative type numbers (@pxref{Negative Type Numbers}).
+
+@item R @var{fp_type} ; @var{bytes} ;
+Define a floating point type. @var{fp_type} has one of the following values:
+
+@table @code
+@item 1 (NF_SINGLE)
+IEEE 32-bit (single precision) floating point format.
+
+@item 2 (NF_DOUBLE)
+IEEE 64-bit (double precision) floating point format.
+
+@item 3 (NF_COMPLEX)
+@item 4 (NF_COMPLEX16)
+@item 5 (NF_COMPLEX32)
+@c "GDB source" really means @file{include/aout/stab_gnu.h}, but trying
+@c to put that here got an overfull hbox.
+These are for complex numbers. A comment in the GDB source describes
+them as Fortran complex, double complex, and complex*16, respectively,
+but what does that mean? (i.e. Single precision? Double precison?).
+
+@item 6 (NF_LDOUBLE)
+Long double. This should probably only be used for Sun format long
+double, and new codes should be used for other floating point formats
+(NF_DOUBLE can be used if a long double is really just an IEEE double,
+of course).
+@end table
+
+@var{bytes} is the number of bytes occupied by the type. This allows a
+debugger to perform some operations with the type even if it doesn't
+understand @var{fp_code}.
+
+@item g @var{type-information} ; @var{nbits}
+Documented by AIX to define a floating type, but their compiler actually
+uses negative type numbers (@pxref{Negative Type Numbers}).
+
+@item c @var{type-information} ; @var{nbits}
+Documented by AIX to define a complex type, but their compiler actually
+uses negative type numbers (@pxref{Negative Type Numbers}).
+@end table
+
+The C @code{void} type is defined as a signed integral type 0 bits long:
+@example
+.stabs "void:t19=bs0;0;0",128,0,0,0
+@end example
+The Solaris compiler seems to omit the trailing semicolon in this case.
+Getting sloppy in this way is not a swift move because if a type is
+embedded in a more complex expression it is necessary to be able to tell
+where it ends.
+
+I'm not sure how a boolean type is represented.
+
+@node Negative Type Numbers
+@subsection Negative Type numbers
+
+Since the debugger knows about the builtin types anyway, the idea of
+negative type numbers is simply to give a special type number which
+indicates the built in type. There is no stab defining these types.
+
+I'm not sure whether anyone has tried to define what this means if
+@code{int} can be other than 32 bits (or other types can be other than
+their customary size). If @code{int} has exactly one size for each
+architecture, then it can be handled easily enough, but if the size of
+@code{int} can vary according the compiler options, then it gets hairy.
+I guess the consistent way to do this would be to define separate
+negative type numbers for 16-bit @code{int} and 32-bit @code{int};
+therefore I have indicated below the customary size (and other format
+information) for each type. The information below is currently correct
+because AIX on the RS6000 is the only system which uses these type
+numbers. If these type numbers start to get used on other systems, I
+suspect the correct thing to do is to define a new number in cases where
+a type does not have the size and format indicated below.
+
+Also note that part of the definition of the negative type number is
+the name of the type. Types with identical size and format but
+different names have different negative type numbers.
+
+@table @code
+@item -1
+@code{int}, 32 bit signed integral type.
+
+@item -2
+@code{char}, 8 bit type holding a character. Both GDB and dbx on AIX
+treat this as signed. GCC uses this type whether @code{char} is signed
+or not, which seems like a bad idea. The AIX compiler (xlc) seems to
+avoid this type; it uses -5 instead for @code{char}.
+
+@item -3
+@code{short}, 16 bit signed integral type.
+
+@item -4
+@code{long}, 32 bit signed integral type.
+
+@item -5
+@code{unsigned char}, 8 bit unsigned integral type.
+
+@item -6
+@code{signed char}, 8 bit signed integral type.
+
+@item -7
+@code{unsigned short}, 16 bit unsigned integral type.
+
+@item -8
+@code{unsigned int}, 32 bit unsigned integral type.
+
+@item -9
+@code{unsigned}, 32 bit unsigned integral type.
+
+@item -10
+@code{unsigned long}, 32 bit unsigned integral type.
+
+@item -11
+@code{void}, type indicating the lack of a value.
+
+@item -12
+@code{float}, IEEE single precision.
+
+@item -13
+@code{double}, IEEE double precision.
+
+@item -14
+@code{long double}, IEEE double precision. The compiler claims the size
+will increase in a future release, and for binary compatibility you have
+to avoid using @code{long double}. I hope when they increase it they
+use a new negative type number.
+
+@item -15
+@code{integer}. 32 bit signed integral type.
+
+@item -16
+@code{boolean}. 32 bit type. How is the truth value encoded? Is it
+the least significant bit or is it a question of whether the whole value
+is zero or non-zero?
+
+@item -17
+@code{short real}. IEEE single precision.
+
+@item -18
+@code{real}. IEEE double precision.
+
+@item -19
+@code{stringptr}. @xref{Strings}.
+
+@item -20
+@code{character}, 8 bit unsigned character type.
+
+@item -21
+@code{logical*1}, 8 bit unsigned integral type.
+
+@item -22
+@code{logical*2}, 16 bit unsigned integral type.
+
+@item -23
+@code{logical*4}, 32 bit unsigned integral type.
+
+@item -24
+@code{logical}, 32 bit unsigned integral type.
+
+@item -25
+@code{complex}. A complex type consisting of two IEEE single-precision
+floating point values.
+
+@item -26
+@code{complex}. A complex type consisting of two IEEE double-precision
+floating point values.
+
+@item -27
+@code{integer*1}, 8 bit signed integral type.
+
+@item -28
+@code{integer*2}, 16 bit signed integral type.
+
+@item -29
+@code{integer*4}, 32 bit signed integral type.
+
+@item -30
+@code{wchar}. Wide character, 16 bits wide, unsigned (what format?
+Unicode?).
+@end table
+
+@node Miscellaneous Types
+@section Miscellaneous Types
+
+@table @code
+@item b @var{type-information} ; @var{bytes}
+Pascal space type. This is documented by IBM; what does it mean?
+
+Note that this use of the @samp{b} type descriptor can be distinguished
+from its use for builtin integral types (@pxref{Builtin Type
+Descriptors}) because the character following the type descriptor is
+always a digit, @samp{(}, or @samp{-}.
+
+@item B @var{type-information}
+A volatile-qualified version of @var{type-information}. This is a Sun
+extension. A volatile-qualified type means that references and stores
+to a variable of that type must not be optimized or cached; they must
+occur as the user specifies them.
+
+@item d @var{type-information}
+File of type @var{type-information}. As far as I know this is only used
+by Pascal.
+
+@item k @var{type-information}
+A const-qualified version of @var{type-information}. This is a Sun
+extension. A const-qualified type means that a variable of this type
+cannot be modified.
+
+@item M @var{type-information} ; @var{length}
+Multiple instance type. The type seems to composed of @var{length}
+repetitions of @var{type-information}, for example @code{character*3} is
+represented by @samp{M-2;3}, where @samp{-2} is a reference to a
+character type (@pxref{Negative Type Numbers}). I'm not sure how this
+differs from an array. This appears to be a FORTRAN feature.
+@var{length} is a bound, like those in range types, @xref{Subranges}.
+
+@item S @var{type-information}
+Pascal set type. @var{type-information} must be a small type such as an
+enumeration or a subrange, and the type is a bitmask whose length is
+specified by the number of elements in @var{type-information}.
+
+@item * @var{type-information}
+Pointer to @var{type-information}.
+@end table
+
+@node Cross-references
+@section Cross-references to other types
+
+If a type is used before it is defined, one common way to deal with this
+is just to use a type reference to a type which has not yet been
+defined. The debugger is expected to be able to deal with this.
+
+Another way is with the @samp{x} type descriptor, which is followed by
+@samp{s} for a structure tag, @samp{u} for a union tag, or @samp{e} for
+a enumerator tag, followed by the name of the tag, followed by @samp{:}.
+for example the following C declarations:
+
+@example
+struct foo;
+struct foo *bar;
+@end example
+
+produce
+
+@example
+.stabs "bar:G16=*17=xsfoo:",32,0,0,0
+@end example
+
+Not all debuggers support the @samp{x} type descriptor, so on some
+machines GCC does not use it. I believe that for the above example it
+would just emit a reference to type 17 and never define it, but I
+haven't verified that.
+
+Modula-2 imported types, at least on AIX, use the @samp{i} type
+descriptor, which is followed by the name of the module from which the
+type is imported, followed by @samp{:}, followed by the name of the
+type. There is then optionally a comma followed by type information for
+the type (This differs from merely naming the type (@pxref{Typedefs}) in
+that it identifies the module; I don't understand whether the name of
+the type given here is always just the same as the name we are giving
+it, or whether this type descriptor is used with a nameless stab
+(@pxref{Stabs Format}), or what). The symbol ends with @samp{;}.
+
+@node Subranges
+@section Subrange types
+
+The @samp{r} type descriptor defines a type as a subrange of another
+type. It is followed by type information for the type which it is a
+subrange of, a semicolon, an integral lower bound, a semicolon, an
+integral upper bound, and a semicolon. The AIX documentation does not
+specify the trailing semicolon, in an effort to specify array indexes
+more cleanly, but a subrange which is not an array index has always
+included a trailing semicolon (@pxref{Arrays}).
+
+Instead of an integer, either bound can be one of the following:
+
+@table @code
+@item A @var{offset}
+The bound is passed by reference on the stack at offset @var{offset}
+from the argument list. @xref{Parameters}, for more information on such
+offsets.
+
+@item T @var{offset}
+The bound is passed by value on the stack at offset @var{offset} from
+the argument list.
+
+@item a @var{register-number}
+The bound is pased by reference in register number
+@var{register-number}.
+
+@item t @var{register-number}
+The bound is passed by value in register number @var{register-number}.
+
+@item J
+There is no bound.
+@end table
+
+Subranges are also used for builtin types, @xref{Traditional Builtin Types}.
+
+@node Arrays
+@section Array types
+
+Arrays use the @samp{a} type descriptor. Following the type descriptor
+is the type of the index and the type of the array elements. If the
+index type is a range type, it will end in a semicolon; if it is not a
+range type (for example, if it is a type reference), there does not
+appear to be any way to tell where the types are separated. In an
+effort to clean up this mess, IBM documents the two types as being
+separated by a semicolon, and a range type as not ending in a semicolon
+(but this is not right for range types which are not array indexes,
+@pxref{Subranges}). I think probably the best solution is to specify
+that a semicolon ends a range type, and that the index type and element
+type of an array are separated by a semicolon, but that if the index
+type is a range type, the extra semicolon can be omitted. GDB (at least
+through version 4.9) doesn't support any kind of index type other than a
+range anyway; I'm not sure about dbx.
+
+It is well established, and widely used, that the type of the index,
+unlike most types found in the stabs, is merely a type definition, not
+type information (@pxref{Stabs Format}) (that is, it need not start with
+@var{type-number}@code{=} if it is defining a new type). According to a
+comment in GDB, this is also true of the type of the array elements; it
+gives @samp{ar1;1;10;ar1;1;10;4} as a legitimate way to express a two
+dimensional array. According to AIX documentation, the element type
+must be type information. GDB accepts either.
+
+The type of the index is often a range type, expressed as the letter r
+and some parameters. It defines the size of the array. In the example
+below, the range @code{r1;0;2;} defines an index type which is a
+subrange of type 1 (integer), with a lower bound of 0 and an upper bound
+of 2. This defines the valid range of subscripts of a three-element C
+array.
+
+For example, the definition
+
+@example
+char char_vec[3] = @{'a','b','c'@};
+@end example
+
+@noindent
+produces the output
+
+@example
+.stabs "char_vec:G19=ar1;0;2;2",32,0,0,0
+ .global _char_vec
+ .align 4
+_char_vec:
+ .byte 97
+ .byte 98
+ .byte 99
+@end example
+
+If an array is @dfn{packed}, it means that the elements are spaced more
+closely than normal, saving memory at the expense of speed. For
+example, an array of 3-byte objects might, if unpacked, have each
+element aligned on a 4-byte boundary, but if packed, have no padding.
+One way to specify that something is packed is with type attributes
+(@pxref{Stabs Format}), in the case of arrays another is to use the
+@samp{P} type descriptor instead of @samp{a}. Other than specifying a
+packed array, @samp{P} is identical to @samp{a}.
+
+@c FIXME-what is it? A pointer?
+An open array is represented by the @samp{A} type descriptor followed by
+type information specifying the type of the array elements.
+
+@c FIXME: what is the format of this type? A pointer to a vector of pointers?
+An N-dimensional dynamic array is represented by
+
+@example
+D @var{dimensions} ; @var{type-information}
+@end example
+
+@c Does dimensions really have this meaning? The AIX documentation
+@c doesn't say.
+@var{dimensions} is the number of dimensions; @var{type-information}
+specifies the type of the array elements.
+
+@c FIXME: what is the format of this type? A pointer to some offsets in
+@c another array?
+A subarray of an N-dimensional array is represented by
+
+@example
+E @var{dimensions} ; @var{type-information}
+@end example
+
+@c Does dimensions really have this meaning? The AIX documentation
+@c doesn't say.
+@var{dimensions} is the number of dimensions; @var{type-information}
+specifies the type of the array elements.
+
+@node Strings
+@section Strings
+
+Some languages, like C or the original Pascal, do not have string types,
+they just have related things like arrays of characters. But most
+Pascals and various other languages have string types, which are
+indicated as follows:
+
+@table @code
+@item n @var{type-information} ; @var{bytes}
+@var{bytes} is the maximum length. I'm not sure what
+@var{type-information} is; I suspect that it means that this is a string
+of @var{type-information} (thus allowing a string of integers, a string
+of wide characters, etc., as well as a string of characters). Not sure
+what the format of this type is. This is an AIX feature.
+
+@item z @var{type-information} ; @var{bytes}
+Just like @samp{n} except that this is a gstring, not an ordinary
+string. I don't know the difference.
+
+@item N
+Pascal Stringptr. What is this? This is an AIX feature.
+@end table
+
+@node Enumerations
+@section Enumerations
+
+Enumerations are defined with the @samp{e} type descriptor.
+
+@c FIXME: Where does this information properly go? Perhaps it is
+@c redundant with something we already explain.
The source line below declares an enumeration type. It is defined at
file scope between the bodies of main and s_proc in example2.c.
-Because the N_LSYM is located after the N_RBRAC that marks the end of
+The type definition is located after the N_RBRAC that marks the end of
the previous procedure's block scope, and before the N_FUN that marks
-the beginning of the next procedure's block scope, the N_LSYM does not
-describe a block local symbol, but a file local one. The source line:
+the beginning of the next procedure's block scope. Therefore it does not
+describe a block local symbol, but a file local one.
+
+The source line:
@example
-29 enum e_places @{first,second=3,last@};
+enum e_places @{first,second=3,last@};
@end example
@noindent
-generates the following stab, located just after the N_RBRAC (close
-brace stab) for main. The type definition is in an N_LSYM stab
-because type definitions are file scope not global scope.
-
-@display
- <128> N_LSYM - local symbol
- .stab "name:sym_dec(type)type_def(22)=sym_desc(enum)
- enum_name:value(0),enum_name:value(3),enum_name:value(4),;",
- N_LSYM, NIL, NIL, NIL
-@end display
+generates the following stab
@example
-104 .stabs "e_places:T22=efirst:0,second:3,last:4,;",128,0,0,0
+.stabs "e_places:T22=efirst:0,second:3,last:4,;",128,0,0,0
@end example
The symbol descriptor (T) says that the stab describes a structure,
the e is a list of the elements of the enumeration. The format is
name:value,. The list of elements ends with a ;.
-@node Structure tags
-@section Structure Tags
+There is no standard way to specify the size of an enumeration type; it
+is determined by the architecture (normally all enumerations types are
+32 bits). There should be a way to specify an enumeration type of
+another size; type attributes would be one way to do this @xref{Stabs
+Format}.
+
+@node Structures
+@section Structures
@table @strong
@item Directive:
@code{.stabs}
@item Type:
-@code{N_LSYM}
+@code{N_LSYM} or @code{C_DECL}
@item Symbol Descriptor:
@code{T}
@item Type Descriptor:
@end table
The following source code declares a structure tag and defines an
-instance of the structure in global scope. Then a typedef equates the
+instance of the structure in global scope. Then a typedef equates the
structure tag with a new type. A seperate stab is generated for the
structure tag, the structure typedef, and the structure instance. The
stabs for the tag and the typedef are emited when the definitions are
struct_bytes
elem_name:type_ref(int),bit_offset,field_bits;
elem_name:type_ref(float),bit_offset,field_bits;
- elem_name:type_def(17)=type_desc(dynamic array) index_type(int);NIL;
- high_bound(7);element_type(char),bit_offset,field_bits;;",
+ elem_name:type_def(17)=type_desc(array)
+ index_type(range of int from 0 to 7);
+ element_type(char),bit_offset,field_bits;;",
N_LSYM,NIL,NIL,NIL
30 .stabs "s_tag:T16=s20s_int:1,0,32;s_float:12,32,32;
definition for an element which is a pointer to type 16.
@node Typedefs
-@section Typedefs
-
-@table @strong
-@item Directive:
-@code{.stabs}
-@item Type:
-@code{N_LSYM}
-@item Symbol Descriptor:
-@code{t}
-@end table
+@section Giving a type a name
-Here is the stab for the typedef equating the structure tag with a
-type.
-
-@display
- <128> N_LSYM - type definition
- .stabs "name:sym_desc(type name)type_ref(struct_tag)",N_LSYM,NIL,NIL,NIL
-@end display
+To give a type a name, use the @samp{t} symbol descriptor. For example,
@example
-31 .stabs "s_typedef:t16",128,0,0,0
+.stabs "s_typedef:t16",128,0,0,0
@end example
-And here is the code generated for the structure variable.
+specifies that @code{s_typedef} refers to type number 16. Such stabs
+have symbol type @code{N_LSYM} or @code{C_DECL}.
-@display
- <32> N_GSYM - global symbol
- .stabs "name:sym_desc(global)type_ref(struct_tag)",N_GSYM,NIL,NIL,NIL
-@end display
-
-@example
-136 .stabs "g_an_s:G16",32,0,0,0
-137 .common _g_an_s,20,"bss"
-@end example
-
-Notice that the structure tag has the same type number as the typedef
-for the structure tag. It is impossible to distinguish between a
-variable of the struct type and one of its typedef by looking at the
-debugging information.
+If instead, you are specifying the tag name for a structure, union, or
+enumeration, use the @samp{T} symbol descriptor instead. I believe C is
+the only language with this feature.
+If the type is an opaque type (I believe this is a Modula-2 feature),
+AIX provides a type descriptor to specify it. The type descriptor is
+@samp{o} and is followed by a name. I don't know what the name
+means---is it always the same as the name of the type, or is this type
+descriptor used with a nameless stab (@pxref{Stabs Format})? There
+optionally follows a comma followed by type information which defines
+the type of this type. If omitted, a semicolon is used in place of the
+comma and the type information, and, the type is much like a generic
+pointer type---it has a known size but little else about it is
+specified.
@node Unions
@section Unions
-@table @strong
-@item Directive:
-@code{.stabs}
-@item Type:
-@code{N_LSYM}
-@item Symbol Descriptor:
-@code{T}
-@item Type Descriptor:
-@code{u}
-@end table
-
Next let's look at unions. In example2 this union type is declared
locally to a procedure and an instance of the union is defined.
@end smallexample
The symbol descriptor, T, following the name: means that the stab
-describes an enumeration struct or type tag. The type descriptor u,
+describes an enumeration, struct or type tag. The type descriptor u,
following the 23= of the type definition, narrows it down to a union
type definition. Following the u is the number of bytes in the union.
After that is a list of union element descriptions. Their format is
130 .stabs "an_u:23",128,0,0,-20
@end example
-@node Function types
+@node Function Types
@section Function types
-@display
-type descriptor f
-@end display
+There are various types for function variables. These types are not
+used in defining functions; see symbol descriptor @samp{f}; they are
+used for things like pointers to functions.
+
+The simple, traditional, type is type descriptor @samp{f} is followed by
+type information for the return type of the function, followed by a
+semicolon.
+
+This does not deal with functions the number and type of whose
+parameters are part of their type, as found in Modula-2 or ANSI C. AIX
+provides extensions to specify these, using the @samp{f}, @samp{F},
+@samp{p}, and @samp{R} type descriptors.
-The last type descriptor in C which remains to be described is used
-for function types. Consider the following source line defining a
-global function pointer.
+First comes the type descriptor. Then, if it is @samp{f} or @samp{F},
+this is a function, and the type information for the return type of the
+function follows, followed by a comma. Then comes the number of
+parameters to the function and a semicolon. Then, for each parameter,
+there is the name of the parameter followed by a colon (this is only
+present for type descriptors @samp{R} and @samp{F} which represent
+Pascal function or procedure parameters), type information for the
+parameter, a comma, @samp{0} if passed by reference or @samp{1} if
+passed by value, and a semicolon. The type definition ends with a
+semicolon.
+
+For example,
@example
-4 int (*g_pf)();
+int (*g_pf)();
@end example
-It generates the following code. Since the variable is not
-initialized, the code is located in the common area at the end of the
-file.
-
-@display
- <32> N_GSYM - global variable
- .stabs "name:sym_desc(global)type_def(24)=ptr_to(25)=
- type_def(func)type_ref(int)
-@end display
+@noindent
+generates the following code:
@example
-134 .stabs "g_pf:G24=*25=f1",32,0,0,0
-135 .common _g_pf,4,"bss"
+.stabs "g_pf:G24=*25=f1",32,0,0,0
+ .common _g_pf,4,"bss"
@end example
-Since the variable is global, the stab type is N_GSYM and the symbol
-descriptor is G. The variable defines a new type, 24, which is a
-pointer to another new type, 25, which is defined as a function
-returning int.
+The variable defines a new type, 24, which is a pointer to another new
+type, 25, which is defined as a function returning int.
-@node Symbol tables
+@node Symbol Tables
@chapter Symbol information in symbol tables
This section examines more closely the format of symbol table entries
215 0000e008 D _g_foo
@end example
-@node GNU Cplusplus stabs
+@node Cplusplus
@chapter GNU C++ stabs
@menu
-* Basic Cplusplus types::
-* Simple classes::
-* Class instance::
-* Methods:: Method definition
-* Protections::
-* Method Modifiers:: (const, volatile, const volatile)
-* Virtual Methods::
-* Inheritence::
-* Virtual Base Classes::
-* Static Members::
+* Basic Cplusplus types::
+* Simple classes::
+* Class instance::
+* Methods:: Method definition
+* Protections::
+* Method Modifiers::
+* Virtual Methods::
+* Inheritence::
+* Virtual Base Classes::
+* Static Members::
@end menu
-
-@subsection Symbol descriptors added for C++ descriptions:
-
-@display
-P - register parameter.
-@end display
-
@subsection type descriptors added for C++ descriptions
@table @code
@item #
method type (two ## if minimal debug)
-@item xs
-cross-reference
+@item @@
+Member (class and variable) type. It is followed by type information
+for the offset basetype, a comma, and type information for the type of
+the field being pointed to. (FIXME: this is acknowledged to be
+gibberish. Can anyone say what really goes here?).
+
+Note that there is a conflict between this and type attributes
+(@pxref{Stabs Format}); both use type descriptor @samp{@@}.
+Fortunately, the @samp{@@} type descriptor used in this C++ sense always
+will be followed by a digit, @samp{(}, or @samp{-}, and type attributes
+never start with those things.
@end table
-
@node Basic Cplusplus types
@section Basic types for C++
@end example
Here is the stab for the `this' pointer implicit argument. The name
-of the `this' pointer is always $t. Type 19, the `this' pointer is
+of the `this' pointer is always `this.' Type 19, the `this' pointer is
defined as a pointer to type 20, baseA, but a stab defining baseA has
not yet been emited. Since the compiler knows it will be emited
shortly, here it just outputs a cross reference to the undefined
type_desc(ptr to)type_ref(baseA)=
type_desc(cross-reference to)baseA:",N_RSYM,NIL,NIL,register_number
-.stabs "$t:P19=*20=xsbaseA:",64,0,0,8
+.stabs "this:P19=*20=xsbaseA:",64,0,0,8
@end example
The stab for the explicit integer argument looks just like a parameter
This is in turn defined as a pointer to another new type (22).
Type 22 is the vtable itself, which is defined as an array, indexed by
-integers, with a high bound of 1, and elements of type 17. Type 17
-was the vtable record type defined by the boilerplate C++ type
-definitions, as shown earlier.
+a range of integers between 0 and 1, and whose elements are of type
+17. Type 17 was the vtable record type defined by the boilerplate C++
+type definitions, as shown earlier.
The bit offset of the vtable pointer field is 32. The number of bits
in the field are not specified when the field is a vtable pointer.
.stabs "class_name(A):type_def(20)=sym_desc(struct)struct_bytes(8)
field_name(Adat):type_ref(int),bit_offset(0),field_bits(32);
field_name(A virt func ptr):type_def(21)=type_desc(ptr to)type_def(22)=
- sym_desc(array)index_type_ref(int);NIL;elem_type_ref(vtbl elem type);
+ sym_desc(array)index_type_ref(range of int from 0 to 1);
+ elem_type_ref(vtbl elem type),
bit_offset(32);
meth_name(A_virt)::typedef(23)=sym_desc(method)returning(int);
:arg_type(int),protection(public)normal(yes)virtual(yes)
N_LSYM,NIL,NIL,NIL
@end display
+@c FIXME: bogus line break.
@example
-.stabs "A:t20=s8Adat:1,0,32;$vf20:21=*22=ar1;0;1;17,32;A_virt::23=##1;:i;2A*-2147483647;20;;;~%20;",128,0,0,0
+.stabs "A:t20=s8Adat:1,0,32;$vf20:21=*22=ar1;0;1;17,32;
+ A_virt::23=##1;:i;2A*-2147483647;20;;;~%20;",128,0,0,0
@end example
@node Inheritence
@c FIXME!!! the linebreaks in the following example probably make the
@c examples literally unusable, but I don't know any other way to get
@c them on the page.
+@c One solution would be to put some of the type definitions into
+@c separate stabs, even if that's not exactly what the compiler actually
+@c emits.
@smallexample
.stabs "A:T20=s8Adat:1,0,32;$vf20:21=*22=ar1;0;1;17,32;
A_virt::23=##1;:i;2A*-2147483647;20;;;~%20;",128,0,0,0
Following the name and a semicolon is a type reference describing the
type of the virtual base class pointer, in this case 24. Type 24 was
-defined earlier as the type of the B class `this` pointer, $t. The
+defined earlier as the type of the B class `this` pointer. The
`this' pointer for a class is a pointer to the class type.
@example
-.stabs "$t:P24=*25=xsB:",64,0,0,8
+.stabs "this:P24=*25=xsB:",64,0,0,8
@end example
Finally the field offset part of the vbase pointer field description
137 .common _g_an_s,20,"bss"
@end example
+@node Stab Types
+@appendix Values for the Stab Type Field
-@node Quick reference
-@appendix Quick reference
+These are all the possible values for the stab type field, for
+@code{a.out} files. This does not apply to XCOFF.
-@menu
-* Stab types:: Table A: Symbol types from stabs
-* Assembler types:: Table B: Symbol types from assembler and linker
-* Symbol descriptors:: Table C
-* Type Descriptors:: Table D
-@end menu
+The following types are used by the linker and assembler; there is
+nothing stabs-specific about them. Since this document does not attempt
+to describe aspects of object file format other than the debugging
+format, no details are given.
-@node Stab types
-@section Table A: Symbol types from stabs
+@c Try to get most of these to fit on a single line.
+@iftex
+@tableindent=1.5in
+@end iftex
-Table A lists stab types sorted by type number. Stab type numbers are
-32 and greater. This is the full list of stab numbers, including stab
-types that are used in languages other than C.
+@table @code
+@item 0x0 N_UNDF
+Undefined symbol
-The #define names for these stab types are defined in:
-devo/include/aout/stab.def
+@item 0x2 N_ABS
+File scope absolute symbol
-@smallexample
-type type #define used to describe
-dec hex name source program feature
-------------------------------------------------
-32 0x20 N_GYSM global symbol
-34 0X22 N_FNAME function name (for BSD Fortran)
-36 0x24 N_FUN function name or text segment variable for C
-38 0x26 N_STSYM static symbol (data segment w/internal linkage)
-40 0x28 N_LCSYM .lcomm symbol(BSS-seg variable w/internal linkage)
-42 0x2a N_MAIN Name of main routine (not used in C)
-48 0x30 N_PC global symbol (for Pascal)
-50 0x32 N_NSYMS number of symbols (according to Ultrix V4.0)
-52 0x34 N_NOMAP no DST map for sym (according to Ultrix V4.0)
-64 0x40 N_RSYM register variable
-66 0x42 N_M2C Modula-2 compilation unit
-68 0x44 N_SLINE line number in text segment
-70 0x46 N_DSLINE line number in data segment
-
-72 0x48 N_BSLINE line number in bss segment
-72 0x48 N_BROWS Sun source code browser, path to .cb file
-
-74 0x4a N_DEFD GNU Modula2 definition module dependency
-
-80 0x50 N_EHDECL GNU C++ exception variable
-80 0x50 N_MOD2 Modula2 info "for imc" (according to Ultrix V4.0)
-
-84 0x54 N_CATCH GNU C++ "catch" clause
-96 0x60 N_SSYM structure of union element
-100 0x64 N_SO path and name of source file
-128 0x80 N_LSYM automatic var in the stack
- (also used for type desc.)
-130 0x82 N_BINCL beginning of an include file (Sun only)
-132 0x84 N_SOL Name of sub-source (#include) file.
-160 0xa0 N_PSYM parameter variable
-162 0xa2 N_EINCL end of an include file
-164 0xa4 N_ENTRY alternate entry point
-192 0xc0 N_LBRAC beginning of a lexical block
-194 0xc2 N_EXCL place holder for a deleted include file
-196 0xc4 N_SCOPE modula2 scope information (Sun linker)
-224 0xe0 N_RBRAC end of a lexical block
-226 0xe2 N_BCOMM begin named common block
-228 0xe4 N_ECOMM end named common block
-232 0xe8 N_ECOML end common (local name)
-
- << used on Gould systems for non-base registers syms >>
-240 0xf0 N_NBTEXT ??
-242 0xf2 N_NBDATA ??
-244 0xf4 N_NBBSS ??
-246 0xf6 N_NBSTS ??
-248 0xf8 N_NBLCS ??
-@end smallexample
+@item 0x3 N_ABS | N_EXT
+External absolute symbol
-@node Assembler types
-@section Table B: Symbol types from assembler and linker
+@item 0x4 N_TEXT
+File scope text symbol
-Table B shows the types of symbol table entries that hold assembler
-and linker symbols.
+@item 0x5 N_TEXT | N_EXT
+External text symbol
-The #define names for these n_types values are defined in
-/include/aout/aout64.h
+@item 0x6 N_DATA
+File scope data symbol
-@smallexample
-dec hex #define
-n_type n_type name used to describe
-------------------------------------------
-1 0x0 N_UNDF undefined symbol
-2 0x2 N_ABS absolute symbol -- defined at a particular address
-3 0x3 extern " (vs. file scope)
-4 0x4 N_TEXT text symbol -- defined at offset in text segment
-5 0x5 extern " (vs. file scope)
-6 0x6 N_DATA data symbol -- defined at offset in data segment
-7 0x7 extern " (vs. file scope)
-8 0x8 N_BSS BSS symbol -- defined at offset in zero'd segment
-9 extern " (vs. file scope)
-
-12 0x0C N_FN_SEQ func name for Sequent compilers (stab exception)
-
-49 0x12 N_COMM common sym -- visable after shared lib dynamic link
-31 0x1f N_FN file name of a .o file
-@end smallexample
+@item 0x7 N_DATA | N_EXT
+External data symbol
-@node Symbol descriptors
-@section Table C: Symbol descriptors
+@item 0x8 N_BSS
+File scope BSS symbol
-@example
-descriptor meaning
--------------------------------------------------
-(empty) local variable
- f local function
- F global function
- G global variable
- p value parameter
- r register variable
- S static global variable
- t type name
- T enumeration, struct or type tag
- V static local variable
-@end example
+@item 0x9 N_BSS | N_EXT
+External BSS symbol
+
+@item 0x0c N_FN_SEQ
+Same as N_FN, for Sequent compilers
+
+@item 0x0a N_INDR
+Symbol is indirected to another symbol
+
+@item 0x12 N_COMM
+Common sym -- visable after shared lib dynamic link
+
+@item 0x14 N_SETA
+Absolute set element
+
+@item 0x16 N_SETT
+Text segment set element
+
+@item 0x18 N_SETD
+Data segment set element
+
+@item 0x1a N_SETB
+BSS segment set element
+
+@item 0x1c N_SETV
+Pointer to set vector
+
+@item 0x1e N_WARNING
+Print a warning message during linking
+
+@item 0x1f N_FN
+File name of a .o file
+@end table
+
+The following symbol types indicate that this is a stab. This is the
+full list of stab numbers, including stab types that are used in
+languages other than C.
+
+@table @code
+@item 0x20 N_GSYM
+Global symbol, @xref{N_GSYM}.
+
+@item 0x22 N_FNAME
+Function name (for BSD Fortran), @xref{N_FNAME}.
+
+@item 0x24 N_FUN
+Function name (@pxref{Procedures}) or text segment variable
+(@pxref{Statics}).
+
+@item 0x26 N_STSYM
+Data segment file-scope variable, @xref{Statics}.
+
+@item 0x28 N_LCSYM
+BSS segment file-scope variable, @xref{Statics}.
+
+@item 0x2a N_MAIN
+Name of main routine, @xref{Main Program}.
+
+@c FIXME: discuss this in the main body of the text where we talk about
+@c using N_FUN for variables.
+@item 0x2c N_ROSYM
+Read-only data symbol (Solaris2). Most systems use N_FUN for this.
+
+@item 0x30 N_PC
+Global symbol (for Pascal), @xref{N_PC}.
+
+@item 0x32 N_NSYMS
+Number of symbols (according to Ultrix V4.0), @xref{N_NSYMS}.
+
+@item 0x34 N_NOMAP
+No DST map for sym (according to Ultrix V4.0), @xref{N_NOMAP}.
+
+@c FIXME: describe this solaris feature in the body of the text (see
+@c comments in include/aout/stab.def).
+@item 0x38 N_OBJ
+Object file (Solaris2).
+
+@c See include/aout/stab.def for (a little) more info.
+@item 0x3c N_OPT
+Debugger options (Solaris2).
+
+@item 0x40 N_RSYM
+Register variable, @xref{N_RSYM}.
+
+@item 0x42 N_M2C
+Modula-2 compilation unit, @xref{N_M2C}.
+
+@item 0x44 N_SLINE
+Line number in text segment, @xref{Line Numbers}.
+
+@item 0x46 N_DSLINE
+Line number in data segment, @xref{Line Numbers}.
+
+@item 0x48 N_BSLINE
+Line number in bss segment, @xref{Line Numbers}.
+
+@item 0x48 N_BROWS
+Sun source code browser, path to .cb file, @xref{N_BROWS}.
+
+@item 0x4a N_DEFD
+Gnu Modula2 definition module dependency, @xref{N_DEFD}.
+
+@item 0x4c N_FLINE
+Function start/body/end line numbers (Solaris2).
+
+@item 0x50 N_EHDECL
+Gnu C++ exception variable, @xref{N_EHDECL}.
+
+@item 0x50 N_MOD2
+Modula2 info "for imc" (according to Ultrix V4.0), @xref{N_MOD2}.
+
+@item 0x54 N_CATCH
+Gnu C++ "catch" clause, @xref{N_CATCH}.
+
+@item 0x60 N_SSYM
+Structure of union element, @xref{N_SSYM}.
+
+@item 0x62 N_ENDM
+Last stab for module (Solaris2).
+
+@item 0x64 N_SO
+Path and name of source file , @xref{Source Files}.
+
+@item 0x80 N_LSYM
+Automatic var in the stack or type definition, @xref{N_LSYM}, @xref{Typedefs}.
+
+@item 0x82 N_BINCL
+Beginning of an include file (Sun only), @xref{Source Files}.
+
+@item 0x84 N_SOL
+Name of include file, @xref{Source Files}.
+
+@item 0xa0 N_PSYM
+Parameter variable, @xref{Parameters}.
+
+@item 0xa2 N_EINCL
+End of an include file, @xref{Source Files}.
+
+@item 0xa4 N_ENTRY
+Alternate entry point, @xref{N_ENTRY}.
+
+@item 0xc0 N_LBRAC
+Beginning of a lexical block, @xref{Block Structure}.
+
+@item 0xc2 N_EXCL
+Place holder for a deleted include file, @xref{Source Files}.
+
+@item 0xc4 N_SCOPE
+Modula2 scope information (Sun linker), @xref{N_SCOPE}.
+
+@item 0xe0 N_RBRAC
+End of a lexical block, @xref{Block Structure}.
+
+@item 0xe2 N_BCOMM
+Begin named common block, @xref{Common Blocks}.
+
+@item 0xe4 N_ECOMM
+End named common block, @xref{Common Blocks}.
+
+@item 0xe8 N_ECOML
+Member of a common block, @xref{Common Blocks}.
+
+@c FIXME: How does this really work? Move it to main body of document.
+@item 0xea N_WITH
+Pascal @code{with} statement: type,,0,0,offset (Solaris2).
+
+@item 0xf0 N_NBTEXT
+Gould non-base registers, @xref{Gould}.
+
+@item 0xf2 N_NBDATA
+Gould non-base registers, @xref{Gould}.
+
+@item 0xf4 N_NBBSS
+Gould non-base registers, @xref{Gould}.
+
+@item 0xf6 N_NBSTS
+Gould non-base registers, @xref{Gould}.
+
+@item 0xf8 N_NBLCS
+Gould non-base registers, @xref{Gould}.
+@end table
+
+@c Restore the default table indent
+@iftex
+@tableindent=.8in
+@end iftex
+
+@node Symbol Descriptors
+@appendix Table of Symbol Descriptors
+
+@c Please keep this alphabetical
+@table @code
+@c In TeX, this looks great, digit is in italics. But makeinfo insists
+@c on putting it in `', not realizing that @var should override @code.
+@c I don't know of any way to make makeinfo do the right thing. Seems
+@c like a makeinfo bug to me.
+@item @var{digit}
+@itemx (
+@itemx -
+Local variable, @xref{Automatic variables}.
+
+@item a
+Parameter passed by reference in register, @xref{Parameters}.
+
+@item c
+Constant, @xref{Constants}.
+
+@item C
+Conformant array bound (Pascal, maybe other languages),
+@xref{Parameters}. Name of a caught exception (GNU C++). These can be
+distinguished because the latter uses N_CATCH and the former uses
+another symbol type.
+
+@item d
+Floating point register variable, @xref{Register variables}.
+
+@item D
+Parameter in floating point register, @xref{Parameters}.
+
+@item f
+File scope function, @xref{Procedures}.
+
+@item F
+Global function, @xref{Procedures}.
+
+@item G
+Global variable, @xref{Global Variables}.
+
+@item i
+@xref{Parameters}.
+
+@item I
+Internal (nested) procedure, @xref{Procedures}.
+
+@item J
+Internal (nested) function, @xref{Procedures}.
+
+@item L
+Label name (documented by AIX, no further information known).
+
+@item m
+Module, @xref{Procedures}.
+
+@item p
+Argument list parameter, @xref{Parameters}.
+
+@item pP
+@xref{Parameters}.
+
+@item pF
+FORTRAN Function parameter, @xref{Parameters}.
+
+@item P
+Unfortunately, three separate meanings have been independently invented
+for this symbol descriptor. At least the GNU and Sun uses can be
+distinguished by the symbol type. Global Procedure (AIX) (symbol type
+used unknown), @xref{Procedures}. Register parameter (GNU) (symbol type
+N_PSYM), @xref{Parameters}. Prototype of function referenced by this
+file (Sun acc) (symbol type N_FUN).
+
+@item Q
+Static Procedure, @xref{Procedures}.
+
+@item R
+Register parameter @xref{Parameters}.
+
+@item r
+Register variable, @xref{Register variables}.
+
+@item S
+File scope variable, @xref{Statics}.
+
+@item t
+Type name, @xref{Typedefs}.
+
+@item T
+enumeration, struct or union tag, @xref{Typedefs}.
+
+@item v
+Parameter passed by reference, @xref{Parameters}.
+
+@item V
+Procedure scope static variable, @xref{Statics}.
+
+@item x
+Conformant array, @xref{Parameters}.
+
+@item X
+Function return variable, @xref{Parameters}.
+@end table
@node Type Descriptors
-@section Table D: Type Descriptors
+@appendix Table of Type Descriptors
-@example
-descriptor meaning
--------------------------------------
-(empty) type reference
- a array type
- e enumeration type
- f function type
- r range type
- s structure type
- u union specifications
- * pointer type
-@end example
+@table @code
+@item @var{digit}
+@itemx (
+Type reference, @xref{Stabs Format}.
+
+@item -
+Reference to builtin type, @xref{Negative Type Numbers}.
+
+@item #
+Method (C++), @xref{Cplusplus}.
+
+@item *
+Pointer, @xref{Miscellaneous Types}.
+
+@item &
+Reference (C++).
+
+@item @@
+Type Attributes (AIX), @xref{Stabs Format}. Member (class and variable)
+type (GNU C++), @xref{Cplusplus}.
+
+@item a
+Array, @xref{Arrays}.
+
+@item A
+Open array, @xref{Arrays}.
+
+@item b
+Pascal space type (AIX), @xref{Miscellaneous Types}. Builtin integer
+type (Sun), @xref{Builtin Type Descriptors}.
+
+@item B
+Volatile-qualified type, @xref{Miscellaneous Types}.
+
+@item c
+Complex builtin type, @xref{Builtin Type Descriptors}.
+
+@item C
+COBOL Picture type. See AIX documentation for details.
+
+@item d
+File type, @xref{Miscellaneous Types}.
+
+@item D
+N-dimensional dynamic array, @xref{Arrays}.
+
+@item e
+Enumeration type, @xref{Enumerations}.
+
+@item E
+N-dimensional subarray, @xref{Arrays}.
+
+@item f
+Function type, @xref{Function Types}.
+
+@item F
+Pascal function parameter, @xref{Function Types}
+
+@item g
+Builtin floating point type, @xref{Builtin Type Descriptors}.
+
+@item G
+COBOL Group. See AIX documentation for details.
+
+@item i
+Imported type, @xref{Cross-references}.
+
+@item k
+Const-qualified type, @xref{Miscellaneous Types}.
+
+@item K
+COBOL File Descriptor. See AIX documentation for details.
+
+@item M
+Multiple instance type, @xref{Miscellaneous Types}.
+@item n
+String type, @xref{Strings}.
+
+@item N
+Stringptr, @xref{Strings}.
+
+@item o
+Opaque type, @xref{Typedefs}.
+
+@item p
+Procedure, @xref{Function Types}.
+
+@item P
+Packed array, @xref{Arrays}.
+
+@item r
+Range type, @xref{Subranges}.
+
+@item R
+Builtin floating type, @xref{Builtin Type Descriptors} (Sun). Pascal
+subroutine parameter, @xref{Function Types} (AIX). Detecting this
+conflict is possible with careful parsing (hint: a Pascal subroutine
+parameter type will always contain a comma, and a builtin type
+descriptor never will).
+
+@item s
+Structure type, @xref{Structures}.
+
+@item S
+Set type, @xref{Miscellaneous Types}.
+
+@item u
+Union, @xref{Unions}.
+
+@item v
+Variant record. This is a Pascal and Modula-2 feature which is like a
+union within a struct in C. See AIX documentation for details.
+
+@item w
+Wide character, @xref{Builtin Type Descriptors}.
+
+@item x
+Cross-reference, @xref{Cross-references}.
+
+@item z
+gstring, @xref{Strings}.
+@end table
@node Expanded reference
@appendix Expanded reference by stab type.
+@c FIXME: This appendix should go away, see N_PSYM or N_SO for an example.
+
+For a full list of stab types, and cross-references to where they are
+described, @xref{Stab Types}. This appendix just duplicates certain
+information from the main body of this document; eventually the
+information will all be in one place.
+
Format of an entry:
The first line is the symbol type expressed in decimal, hexadecimal,
Finally, any further information.
@menu
-* N_GSYM:: Global variable
-* N_FNAME:: Function name (BSD Fortran)
-* N_FUN:: C Function name or text segment variable
-* N_STSYM:: Initialized static symbol
-* N_LCSYM:: Uninitialized static symbol
-* N_MAIN:: Name of main routine (not for C)
-* N_PC:: Pascal global symbol
-* N_NSYMS:: Number of symbols
-* N_NOMAP:: No DST map
-* N_RSYM:: Register variable
-* N_M2C:: Modula-2 compilation unit
-* N_SLINE:: Line number in text segment
-* N_DSLINE:: Line number in data segment
-* N_BSLINE:: Line number in bss segment
-* N_BROWS:: Path to .cb file for Sun source code browser
-* N_DEFD:: GNU Modula2 definition module dependency
-* N_EHDECL:: GNU C++ exception variable
-* N_MOD2:: Modula2 information "for imc"
-* N_CATCH:: GNU C++ "catch" clause
-* N_SSYM:: Structure or union element
-* N_SO:: Source file containing main
-* N_LSYM:: Automatic variable
-* N_BINCL:: Beginning of include file (Sun only)
-* N_SOL:: Name of include file
-* N_PSYM:: Parameter variable
-* N_EINCL:: End of include file
-* N_ENTRY:: Alternate entry point
-* N_LBRAC:: Beginning of lexical block
-* N_EXCL:: Deleted include file
-* N_SCOPE:: Modula2 scope information (Sun only)
-* N_RBRAC:: End of lexical block
-* N_BCOMM:: Begin named common block
-* N_ECOMM:: End named common block
-* N_ECOML:: End common
-* Gould:: non-base register symbols used on Gould systems
-* N_LENG:: Length of preceding entry
+* N_GSYM:: Global variable
+* N_FNAME:: Function name (BSD Fortran)
+* N_PC:: Pascal global symbol
+* N_NSYMS:: Number of symbols
+* N_NOMAP:: No DST map
+* N_RSYM:: Register variable
+* N_M2C:: Modula-2 compilation unit
+* N_BROWS:: Path to .cb file for Sun source code browser
+* N_DEFD:: GNU Modula2 definition module dependency
+* N_EHDECL:: GNU C++ exception variable
+* N_MOD2:: Modula2 information "for imc"
+* N_CATCH:: GNU C++ "catch" clause
+* N_SSYM:: Structure or union element
+* N_LSYM:: Automatic variable
+* N_ENTRY:: Alternate entry point
+* N_SCOPE:: Modula2 scope information (Sun only)
+* Gould:: non-base register symbols used on Gould systems
+* N_LENG:: Length of preceding entry
@end menu
@node N_GSYM
# -> G
@end example
-Only the "name" field is significant. the location of the variable is
+Only the "name" field is significant. The location of the variable is
obtained from the corresponding external symbol.
@node N_FNAME
Only the "name" field is significant. The location of the symbol is
obtained from the corresponding extern symbol.
-@node N_FUN
-@section 36 - 0x24 - N_FUN
-Function name or text segment variable for C.
-
-@display
-.stabs "name", N_FUN, NIL, desc, value
-@end display
-
-@example
-@exdent @emph{For functions:}
-"name" -> "proc_name:#return_type"
- # -> F (global function)
- f (local function)
-desc -> line num for proc start. (GCC doesn't set and DBX doesn't miss it.)
-value -> Code address of proc start.
-
-@exdent @emph{For text segment variables:}
-<<How to create one?>>
-@end example
-
-@node N_STSYM
-@section 38 - 0x26 - N_STSYM
-Initialized static symbol (data segment w/internal linkage).
-
-@display
-.stabs "name", N_STSYM, NIL, NIL, value
-@end display
-
-@example
-"name" -> "symbol_name#type"
- # -> S (scope global to compilation unit)
- -> V (scope local to a procedure)
-value -> Data Address
-@end example
-
-@node N_LCSYM
-@section 40 - 0x28 - N_LCSYM
-Unitialized static (.lcomm) symbol(BSS segment w/internal linkage).
-
-@display
-.stabs "name", N_LCLSYM, NIL, NIL, value
-@end display
-
-@example
-"name" -> "symbol_name#type"
- # -> S (scope global to compilation unit)
- -> V (scope local to procedure)
-value -> BSS Address
-@end example
-
-@node N_MAIN
-@section 42 - 0x2a - N_MAIN
-Name of main routine (not used in C)
-
-@display
-.stabs "name", N_MAIN, NIL, NIL, NIL
-@end display
-
-@example
-"name" -> "name_of_main_routine"
-@end example
-
@node N_PC
@section 48 - 0x30 - N_PC
Global symbol (for Pascal)
1 (any other unit)
@end example
-@node N_SLINE
-@section 68 - 0x44 - N_SLINE
-Line number in text segment
-
-@display
-.stabn N_SLINE, 0, desc, value
-@end display
-
-@example
-desc -> line_number
-value -> code_address (relocatable addr where the corresponding code starts)
-@end example
-
-For single source lines that generate discontiguous code, such as flow
-of control statements, there may be more than one N_SLINE stab for the
-same source line. In this case there is a stab at the start of each
-code range, each with the same line number.
-
-@node N_DSLINE
-@section 70 - 0x46 - N_DSLINE
-Line number in data segment
-
-@display
-.stabn N_DSLINE, 0, desc, value
-@end display
-
-@example
-desc -> line_number
-value -> data_address (relocatable addr where the corresponding code
-starts)
-@end example
-
-See comment for N_SLINE above.
-
-@node N_BSLINE
-@section 72 - 0x48 - N_BSLINE
-Line number in bss segment
-
-@display
-.stabn N_BSLINE, 0, desc, value
-@end display
-
-@example
-desc -> line_number
-value -> bss_address (relocatable addr where the corresponding code
-starts)
-@end example
-
-See comment for N_SLINE above.
-
@node N_BROWS
@section 72 - 0x48 - N_BROWS
Sun source code browser, path to .cb file
<<?looking at structs and unions in C I didn't see these>>
-@node N_SO
-@section 100 - 0x64 - N_SO
-Path and name of source file containing main routine
-
-@display
-.stabs "name", N_SO, NIL, NIL, value
-@end display
-
-@example
-"name" -> /path/to/source/file
- -> source_file_terminal_name
-
-value -> the starting text address of the compilation.
-@end example
-
-These are found two in a row. The name field of the first N_SO
-contains the path to the source file. The name field of the second
-N_SO contains the terminal name of the source file itself.
-
@node N_LSYM
@section 128 - 0x80 - N_LSYM
Automatic var in the stack (also used for type descriptors.)
defines the type. See the Table D for type descriptors and the
section on types for what data follows each type descriptor.
-@node N_BINCL
-@section 130 - 0x82 - N_BINCL
-
-Beginning of an include file (Sun only)
-
-Beginning of an include file. Only Sun uses this. In an object file,
-only the name is significant. The Sun linker puts data into some of
-the other fields.
-
-@node N_SOL
-@section 132 - 0x84 - N_SOL
-
-Name of a sub-source file (#include file). Value is starting address
-of the compilation.
-<<?>>
-
-@node N_PSYM
-@section 160 - 0xa0 - N_PSYM
-
-Parameter variable
-
-@display
-stabs. "name", N_PSYM, NIL, NIL, value
-@end display
-
-@example
-"name" -> "param_name:#type"
- # -> p (value parameter)
- -> i (value parameter by reference, indirect access)
- -> v (variable parameter by reference)
- -> C ( read-only parameter, conformant array bound)
- -> x (confomant array value parameter)
- -> pP (<<??>>)
- -> pF (<<??>>)
- -> X (function result variable)
- -> b (based variable)
-
-value -> offset from the argument pointer (positive).
-@end example
-
-On most machines the argument pointer is the same as the frame
-pointer.
-
-@node N_EINCL
-@section 162 - 0xa2 - N_EINCL
-
-End of an include file. This and N_BINCL act as brackets around the
-file's output. In an ojbect file, there is no significant data in
-this entry. The Sun linker puts data into some of the fields.
-<<?>>
-
@node N_ENTRY
@section 164 - 0xa4 - N_ENTRY
Value is its address.
<<?>>
-@node N_LBRAC
-@section 192 - 0xc0 - N_LBRAC
-
-Beginning of a lexical block (left brace). The variable defined
-inside the block precede the N_LBRAC symbol. Or can they follow as
-well as long as a new N_FUNC was not encountered. <<?>>
-
-@display
-.stabn N_LBRAC, NIL, NIL, value
-@end display
-
-@example
-value -> code address of block start.
-@end example
-
-@node N_EXCL
-@section 194 - 0xc2 - N_EXCL
-
-Place holder for a deleted include file. Replaces a N_BINCL and
-everything up to the corresponding N_EINCL. The Sun linker generates
-these when it finds multiple indentical copies of the symbols from an
-included file. This appears only in output from the Sun linker.
-<<?>>
-
@node N_SCOPE
@section 196 - 0xc4 - N_SCOPE
Modula2 scope information (Sun linker)
<<?>>
-@node N_RBRAC
-@section 224 - 0xe0 - N_RBRAC
-
-End of a lexical block (right brace)
-
-@display
-.stabn N_RBRAC, NIL, NIL, value
-@end display
-
-@example
-value -> code address of the end of the block.
-@end example
-
-@node N_BCOMM
-@section 226 - 0xe2 - N_BCOMM
-
-Begin named common block.
-
-Only the name is significant.
-<<?>>
-
-@node N_ECOMM
-@section 228 - 0xe4 - N_ECOMM
-
-End named common block.
-
-Only the name is significant and it should match the N_BCOMM
-<<?>>
-
-@node N_ECOML
-@section 232 - 0xe8 - N_ECOML
-
-End common (local name)
-
-value is address.
-<<?>>
-
@node Gould
@section Non-base registers on Gould systems
-<< used on Gould systems for non-base registers syms, values assigned
-at random, need real info from Gould. >>
-<<?>>
+
+These are used on Gould systems for non-base registers syms.
+
+However, the following values are not the values used by Gould; they are
+the values which GNU has been documenting for these values for a long
+time, without actually checking what Gould uses. I include these values
+only because perhaps some someone actually did something with the GNU
+information (I hope not, why GNU knowingly assigned wrong values to
+these in the header file is a complete mystery to me).
@example
240 0xf0 N_NBTEXT ??
N_RBRAC of the preceding function and before the code of the
procedure in which they are defined. This is exactly the same as
types defined in the source file between the two procedure bodies.
-GDB overcompensates by placing all types in block #1 the block for
+GDB overcompensates by placing all types in block #1, the block for
symbols of file scope. This is true for default, -ansi and
--traditional compiler options. (p0001063-gcc, p0001066-gdb)
+-traditional compiler options. (Bugs gcc/1063, gdb/1066.)
@item
What ends the procedure scope? Is it the proc block's N_RBRAC or the
next N_FUN? (I believe its the first.)
@item
-The comment in xcoff.h says DBX_STATIC_CONST_VAR_CODE is used for
-static const variables. DBX_STATIC_CONST_VAR_CODE is set to N_FUN by
-default, in dbxout.c. If included, xcoff.h redefines it to N_STSYM.
-But testing the default behaviour, my Sun4 native example shows
-N_STSYM not N_FUN is used to describe file static initialized
-variables. (the code tests for TREE_READONLY(decl) &&
-!TREE_THIS_VOLATILE(decl) and if true uses DBX_STATIC_CONST_VAR_CODE).
-
-@item
+@c FIXME: This should go with the other stuff about global variables.
Global variable stabs don't have location information. This comes
from the external symbol for the same variable. The external symbol
has a leading underbar on the _name of the variable and the stab does
not. How do we know these two symbol table entries are talking about
-the same symbol when their names are different?
+the same symbol when their names are different? (Answer: the debugger
+knows that external symbols have leading underbars).
+@c FIXME: This is absurdly vague; there all kinds of differences, some
+@c of which are the same between gnu & sun, and some of which aren't.
@item
Can gcc be configured to output stabs the way the Sun compiler
does, so that their native debugging tools work? <NO?> It doesn't by
@node xcoff-differences
@appendix Differences between GNU stabs in a.out and GNU stabs in xcoff
-(The AIX/RS6000 native object file format is xcoff with stabs)
+@c FIXME: Merge *all* these into the main body of the document.
+(The AIX/RS6000 native object file format is xcoff with stabs). This
+appendix only covers those differences which are not covered in the main
+body of this document.
@itemize @bullet
-@item
-Instead of .stabs, xcoff uses .stabx.
-
-@item
-The data fields of an xcoff .stabx are in a different order than an
-a.out .stabs. The order is: string, value, type. The desc and null
-fields present in a.out stabs are missing in xcoff stabs. For N_GSYM
-the value field is the name of the symbol.
-
@item
BSD a.out stab types correspond to AIX xcoff storage classes. In general the
mapping is N_STABTYPE becomes C_STABTYPE. Some stab types in a.out
are not supported in xcoff. See Table E. for full mappings.
+@c FIXME: Get C_* types for the block, figure out whether it is always
+@c used (I suspect not), explain clearly, and move to node Statics.
exception:
initialised static N_STSYM and un-initialized static N_LCSYM both map
to the C_STSYM storage class. But the destinction is preserved
block. Begin the block with .bs s[RW] data_section_name for N_STSYM
or .bs s bss_section_name for N_LCSYM. End the block with .es
-@item
-xcoff stabs describing tags and typedefs use the N_DECL (0x8c)instead
-of N_LSYM stab type.
-
-@item
-xcoff uses N_RPSYM (0x8e) instead of the N_RSYM stab type for register
-variables. If the register variable is also a value parameter, then
-use R instead of P for the symbol descriptor.
-
-6.
-xcoff uses negative numbers as type references to the basic types.
-There are no boilerplate type definitions emited for these basic
-types. << make table of basic types and type numbers for C >>
-
-@item
-xcoff .stabx sometimes don't have the name part of the string field.
-
-@item
-xcoff uses a .file stab type to represent the source file name. There
-is no stab for the path to the source file.
-
-@item
-xcoff uses a .line stab type to represent source lines. The format
-is: .line line_number.
-
-@item
-xcoff emits line numbers relative to the start of the current
-function. The start of a function is marked by .bf. If a function
-includes lines from a seperate file, then those line numbers are
-absolute line numbers in the <<sub-?>> file being compiled.
-
-@item
-The start of current include file is marked with: .bi "filename" and
-the end marked with .ei "filename"
-
+@c FIXME: I think they are trying to say something about whether the
+@c assembler defaults the value to the location counter.
@item
If the xcoff stab is a N_FUN (C_FUN) then follow the string field with
,. instead of just ,
-
-@item
-The symbol descriptor for register parameters is P for a.out and R for
-xcoff.
@end itemize
-
(I think that's it for .s file differences. They could stand to be
better presented. This is just a list of what I have noticed so far.
There are a *lot* of differences in the information in the symbol
@node Sun-differences
@appendix Differences between GNU stabs and Sun native stabs.
+@c FIXME: Merge all this stuff into the main body of the document.
+
@itemize @bullet
@item
GNU C stabs define *all* types, file or procedure scope, as
N_LSYM. Sun doc talks about using N_GSYM too.
-@item
-GNU C stabs use `ar' as type descriptor when defining arrays vs. just
-`a' in Sun doc.
-
-@item
-Stabs describing block scopes, N_LBRAC and N_RBRAC are supposed to
-contain the nesting level of the block in the desc field, re Sun doc.
-GNU stabs always have 0 in that field.
-
@item
Sun C stabs use type number pairs in the format (a,b) where a is a
number starting with 1 and incremented for each sub-source file in the
alone, with no source file number.
@end itemize
+@node Stabs-in-elf
+@appendix Using stabs with the ELF object file format.
+
+The ELF object file format allows tools to create object files with custom
+sections containing any arbitrary data. To use stabs in ELF object files,
+the tools create two custom sections, a ".stab" section which contains
+an array of fixed length structures, one struct per stab, and a ".stabstr"
+section containing all the variable length strings that are referenced by
+stabs in the ".stab" section. The byte order of the stabs binary data
+matches the byte order of the ELF file itself, as determined from the
+EI_DATA field in the e_ident member of the ELF header.
+
+The first stab in the ".stab" section for each object file is a "synthetic
+stab", generated entirely by the assembler, with no corresponding ".stab"
+directive as input to the assembler. This stab contains the following
+fields:
+
+@itemize @bullet
+@item
+Offset in the ".stabstr" section to the source filename.
+
+@item
+N_UNDF
+
+@item
+Unused field, always zero.
+
+@item
+Count of upcoming symbols. I.E. the number of remaining stabs for this
+object module.
+
+@item
+Size of the string table fragment associated with this object module, in
+bytes.
+
+@end itemize
+
+The ".stabstr" section always starts with a null byte (so that string
+offsets of zero reference a null string), followed by random length strings,
+each of which is null byte terminated.
+
+The ELF section header for the ".stab" section has it's sh_link member set
+to the section number of the ".stabstr" section, and the ".stabstr" section
+has it's ELF section header sh_type member set to SHT_STRTAB to mark it as
+a string table.
+
@contents
@bye
projects / deliverable / binutils-gdb.git / blobdiff