+@ifset WIN32
+@ifclear GENERIC
+@raisesections
+@end ifclear
+
+@node WIN32
+@section @command{ld} and WIN32 (cygwin/mingw)
+
+This section describes some of the win32 specific @command{ld} issues.
+See @ref{Options,,Command Line Options} for detailed decription of the
+command line options mentioned here.
+
+@table @emph
+@cindex import libraries
+@item import libraries
+The standard Windows linker creates and uses so-called import
+libraries, which contains information for linking to dll's. They are
+regular static archives and are handled as any other static
+archive. The cygwin and mingw ports of @command{ld} have specific
+support for creating such libraries provided with the
+@samp{--out-implib} command line option.
+
+@item exporting DLL symbols
+@cindex exporting DLL symbols
+The cygwin/mingw @command{ld} has several ways to export symbols for dll's.
+
+@table @emph
+@item using auto-export functionality
+@cindex using auto-export functionality
+By default @command{ld} exports symbols with the auto-export functionality,
+which is controlled by the following command line options:
+
+@itemize
+@item --export-all-symbols [This is the default]
+@item --exclude-symbols
+@item --exclude-libs
+@end itemize
+
+If, however, @samp{--export-all-symbols} is not given explicitly on the
+command line, then the default auto-export behavior will be @emph{disabled}
+if either of the following are true:
+
+@itemize
+@item A DEF file is used.
+@item Any symbol in any object file was marked with the __declspec(dllexport) attribute.
+@end itemize
+
+@item using a DEF file
+@cindex using a DEF file
+Another way of exporting symbols is using a DEF file. A DEF file is
+an ASCII file containing definitions of symbols which should be
+exported when a dll is created. Usually it is named @samp{<dll
+name>.def} and is added as any other object file to the linker's
+command line. The file's name must end in @samp{.def} or @samp{.DEF}.
+
+@example
+gcc -o <output> <objectfiles> <dll name>.def
+@end example
+
+Using a DEF file turns off the normal auto-export behavior, unless the
+@samp{--export-all-symbols} option is also used.
+
+Here is an example of a DEF file for a shared library called @samp{xyz.dll}:
+
+@example
+LIBRARY "xyz.dll" BASE=0x20000000
+
+EXPORTS
+foo
+bar
+_bar = bar
+another_foo = abc.dll.afoo
+var1 DATA
+@end example
+
+This example defines a DLL with a non-default base address and five
+symbols in the export table. The third exported symbol @code{_bar} is an
+alias for the second. The fourth symbol, @code{another_foo} is resolved
+by "forwarding" to another module and treating it as an alias for
+@code{afoo} exported from the DLL @samp{abc.dll}. The final symbol
+@code{var1} is declared to be a data object.
+
+The optional @code{LIBRARY <name>} command indicates the @emph{internal}
+name of the output DLL. If @samp{<name>} does not include a suffix,
+the default library suffix, @samp{.DLL} is appended.
+
+When the .DEF file is used to build an application. rather than a
+library, the @code{NAME <name>} command shoud be used instead of
+@code{LIBRARY}. If @samp{<name>} does not include a suffix, the default
+executable suffix, @samp{.EXE} is appended.
+
+With either @code{LIBRARY <name>} or @code{NAME <name>} the optional
+specification @code{BASE = <number>} may be used to specify a
+non-default base address for the image.
+
+If neither @code{LIBRARY <name>} nor @code{NAME <name>} is specified,
+or they specify an empty string, the internal name is the same as the
+filename specified on the command line.
+
+The complete specification of an export symbol is:
+
+@example
+EXPORTS
+ ( ( ( <name1> [ = <name2> ] )
+ | ( <name1> = <module-name> . <external-name>))
+ [ @@ <integer> ] [NONAME] [DATA] [CONSTANT] [PRIVATE] ) *
+@end example
+
+Declares @samp{<name1>} as an exported symbol from the DLL, or declares
+@samp{<name1>} as an exported alias for @samp{<name2>}; or declares
+@samp{<name1>} as a "forward" alias for the symbol
+@samp{<external-name>} in the DLL @samp{<module-name>}.
+Optionally, the symbol may be exported by the specified ordinal
+@samp{<integer>} alias.
+
+The optional keywords that follow the declaration indicate:
+
+@code{NONAME}: Do not put the symbol name in the DLL's export table. It
+will still be exported by its ordinal alias (either the value specified
+by the .def specification or, otherwise, the value assigned by the
+linker). The symbol name, however, does remain visible in the import
+library (if any), unless @code{PRIVATE} is also specified.
+
+@code{DATA}: The symbol is a variable or object, rather than a function.
+The import lib will export only an indirect reference to @code{foo} as
+the symbol @code{_imp__foo} (ie, @code{foo} must be resolved as
+@code{*_imp__foo}).
+
+@code{CONSTANT}: Like @code{DATA}, but put the undecorated @code{foo} as
+well as @code{_imp__foo} into the import library. Both refer to the
+read-only import address table's pointer to the variable, not to the
+variable itself. This can be dangerous. If the user code fails to add
+the @code{dllimport} attribute and also fails to explicitly add the
+extra indirection that the use of the attribute enforces, the
+application will behave unexpectedly.
+
+@code{PRIVATE}: Put the symbol in the DLL's export table, but do not put
+it into the static import library used to resolve imports at link time. The
+symbol can still be imported using the @code{LoadLibrary/GetProcAddress}
+API at runtime or by by using the GNU ld extension of linking directly to
+the DLL without an import library.
+
+See ld/deffilep.y in the binutils sources for the full specification of
+other DEF file statements
+
+@cindex creating a DEF file
+While linking a shared dll, @command{ld} is able to create a DEF file
+with the @samp{--output-def <file>} command line option.
+
+@item Using decorations
+@cindex Using decorations
+Another way of marking symbols for export is to modify the source code
+itself, so that when building the DLL each symbol to be exported is
+declared as:
+
+@example
+__declspec(dllexport) int a_variable
+__declspec(dllexport) void a_function(int with_args)
+@end example
+
+All such symbols will be exported from the DLL. If, however,
+any of the object files in the DLL contain symbols decorated in
+this way, then the normal auto-export behavior is disabled, unless
+the @samp{--export-all-symbols} option is also used.
+
+Note that object files that wish to access these symbols must @emph{not}
+decorate them with dllexport. Instead, they should use dllimport,
+instead:
+
+@example
+__declspec(dllimport) int a_variable
+__declspec(dllimport) void a_function(int with_args)
+@end example
+
+This complicates the structure of library header files, because
+when included by the library itself the header must declare the
+variables and functions as dllexport, but when included by client
+code the header must declare them as dllimport. There are a number
+of idioms that are typically used to do this; often client code can
+omit the __declspec() declaration completely. See
+@samp{--enable-auto-import} and @samp{automatic data imports} for more
+imformation.
+@end table
+
+@cindex automatic data imports
+@item automatic data imports
+The standard Windows dll format supports data imports from dlls only
+by adding special decorations (dllimport/dllexport), which let the
+compiler produce specific assembler instructions to deal with this
+issue. This increases the effort necessary to port existing Un*x
+code to these platforms, especially for large
+c++ libraries and applications. The auto-import feature, which was
+initially provided by Paul Sokolovsky, allows one to omit the
+decorations to archieve a behavior that conforms to that on POSIX/Un*x
+platforms. This feature is enabled with the @samp{--enable-auto-import}
+command-line option, although it is enabled by default on cygwin/mingw.
+The @samp{--enable-auto-import} option itself now serves mainly to
+suppress any warnings that are ordinarily emitted when linked objects
+trigger the feature's use.
+
+auto-import of variables does not always work flawlessly without
+additional assistance. Sometimes, you will see this message
+
+"variable '<var>' can't be auto-imported. Please read the
+documentation for ld's @code{--enable-auto-import} for details."
+
+The @samp{--enable-auto-import} documentation explains why this error
+occurs, and several methods that can be used to overcome this difficulty.
+One of these methods is the @emph{runtime pseudo-relocs} feature, described
+below.
+
+@cindex runtime pseudo-relocation
+For complex variables imported from DLLs (such as structs or classes),
+object files typically contain a base address for the variable and an
+offset (@emph{addend}) within the variable--to specify a particular
+field or public member, for instance. Unfortunately, the runtime loader used
+in win32 environments is incapable of fixing these references at runtime
+without the additional information supplied by dllimport/dllexport decorations.
+The standard auto-import feature described above is unable to resolve these
+references.
+
+The @samp{--enable-runtime-pseudo-relocs} switch allows these references to
+be resolved without error, while leaving the task of adjusting the references
+themselves (with their non-zero addends) to specialized code provided by the
+runtime environment. Recent versions of the cygwin and mingw environments and
+compilers provide this runtime support; older versions do not. However, the
+support is only necessary on the developer's platform; the compiled result will
+run without error on an older system.
+
+@samp{--enable-runtime-pseudo-relocs} is not the default; it must be explicitly
+enabled as needed.
+
+@cindex direct linking to a dll
+@item direct linking to a dll
+The cygwin/mingw ports of @command{ld} support the direct linking,
+including data symbols, to a dll without the usage of any import
+libraries. This is much faster and uses much less memory than does the
+traditional import library method, expecially when linking large
+libraries or applications. When @command{ld} creates an import lib, each
+function or variable exported from the dll is stored in its own bfd, even
+though a single bfd could contain many exports. The overhead involved in
+storing, loading, and processing so many bfd's is quite large, and explains the
+tremendous time, memory, and storage needed to link against particularly
+large or complex libraries when using import libs.
+
+Linking directly to a dll uses no extra command-line switches other than
+@samp{-L} and @samp{-l}, because @command{ld} already searches for a number
+of names to match each library. All that is needed from the developer's
+perspective is an understanding of this search, in order to force ld to
+select the dll instead of an import library.
+
+
+For instance, when ld is called with the argument @samp{-lxxx} it will attempt
+to find, in the first directory of its search path,
+
+@example
+libxxx.dll.a
+xxx.dll.a
+libxxx.a
+cygxxx.dll (*)
+libxxx.dll
+xxx.dll
+@end example
+
+before moving on to the next directory in the search path.
+
+(*) Actually, this is not @samp{cygxxx.dll} but in fact is @samp{<prefix>xxx.dll},
+where @samp{<prefix>} is set by the @command{ld} option
+@samp{--dll-search-prefix=<prefix>}. In the case of cygwin, the standard gcc spec
+file includes @samp{--dll-search-prefix=cyg}, so in effect we actually search for
+@samp{cygxxx.dll}.
+
+Other win32-based unix environments, such as mingw or pw32, may use other
+@samp{<prefix>}es, although at present only cygwin makes use of this feature. It
+was originally intended to help avoid name conflicts among dll's built for the
+various win32/un*x environments, so that (for example) two versions of a zlib dll
+could coexist on the same machine.
+
+The generic cygwin/mingw path layout uses a @samp{bin} directory for
+applications and dll's and a @samp{lib} directory for the import
+libraries (using cygwin nomenclature):
+
+@example
+bin/
+ cygxxx.dll
+lib/
+ libxxx.dll.a (in case of dll's)
+ libxxx.a (in case of static archive)
+@end example
+
+Linking directly to a dll without using the import library can be
+done two ways:
+
+1. Use the dll directly by adding the @samp{bin} path to the link line
+@example
+gcc -Wl,-verbose -o a.exe -L../bin/ -lxxx
+@end example
+
+However, as the dll's often have version numbers appended to their names
+(@samp{cygncurses-5.dll}) this will often fail, unless one specifies
+@samp{-L../bin -lncurses-5} to include the version. Import libs are generally
+not versioned, and do not have this difficulty.
+
+2. Create a symbolic link from the dll to a file in the @samp{lib}
+directory according to the above mentioned search pattern. This
+should be used to avoid unwanted changes in the tools needed for
+making the app/dll.
+
+@example
+ln -s bin/cygxxx.dll lib/[cyg|lib|]xxx.dll[.a]
+@end example
+
+Then you can link without any make environment changes.
+
+@example
+gcc -Wl,-verbose -o a.exe -L../lib/ -lxxx
+@end example
+
+This technique also avoids the version number problems, because the following is
+perfectly legal
+
+@example
+bin/
+ cygxxx-5.dll
+lib/
+ libxxx.dll.a -> ../bin/cygxxx-5.dll
+@end example
+
+Linking directly to a dll without using an import lib will work
+even when auto-import features are exercised, and even when
+@samp{--enable-runtime-pseudo-relocs} is used.
+
+Given the improvements in speed and memory usage, one might justifiably
+wonder why import libraries are used at all. There are two reasons:
+
+1. Until recently, the link-directly-to-dll functionality did @emph{not}
+work with auto-imported data.
+
+2. Sometimes it is necessary to include pure static objects within the
+import library (which otherwise contains only bfd's for indirection
+symbols that point to the exports of a dll). Again, the import lib
+for the cygwin kernel makes use of this ability, and it is not
+possible to do this without an import lib.
+
+So, import libs are not going away. But the ability to replace
+true import libs with a simple symbolic link to (or a copy of)
+a dll, in most cases, is a useful addition to the suite of tools
+binutils makes available to the win32 developer. Given the
+massive improvements in memory requirements during linking, storage
+requirements, and linking speed, we expect that many developers
+will soon begin to use this feature whenever possible.
+
+@item symbol aliasing
+@table @emph
+@item adding additional names
+Sometimes, it is useful to export symbols with additional names.
+A symbol @samp{foo} will be exported as @samp{foo}, but it can also be
+exported as @samp{_foo} by using special directives in the DEF file
+when creating the dll. This will affect also the optional created
+import library. Consider the following DEF file:
+
+@example
+LIBRARY "xyz.dll" BASE=0x61000000
+
+EXPORTS
+foo
+_foo = foo
+@end example
+
+The line @samp{_foo = foo} maps the symbol @samp{foo} to @samp{_foo}.
+
+Another method for creating a symbol alias is to create it in the
+source code using the "weak" attribute:
+
+@example
+void foo () @{ /* Do something. */; @}
+void _foo () __attribute__ ((weak, alias ("foo")));
+@end example
+
+See the gcc manual for more information about attributes and weak
+symbols.
+
+@item renaming symbols
+Sometimes it is useful to rename exports. For instance, the cygwin
+kernel does this regularly. A symbol @samp{_foo} can be exported as
+@samp{foo} but not as @samp{_foo} by using special directives in the
+DEF file. (This will also affect the import library, if it is
+created). In the following example:
+
+@example
+LIBRARY "xyz.dll" BASE=0x61000000
+
+EXPORTS
+_foo = foo
+@end example
+
+The line @samp{_foo = foo} maps the exported symbol @samp{foo} to
+@samp{_foo}.
+@end table
+
+Note: using a DEF file disables the default auto-export behavior,
+unless the @samp{--export-all-symbols} command line option is used.
+If, however, you are trying to rename symbols, then you should list
+@emph{all} desired exports in the DEF file, including the symbols
+that are not being renamed, and do @emph{not} use the
+@samp{--export-all-symbols} option. If you list only the
+renamed symbols in the DEF file, and use @samp{--export-all-symbols}
+to handle the other symbols, then the both the new names @emph{and}
+the original names for the renamed symbols will be exported.
+In effect, you'd be aliasing those symbols, not renaming them,
+which is probably not what you wanted.
+
+@cindex weak externals
+@item weak externals
+The Windows object format, PE, specifies a form of weak symbols called
+weak externals. When a weak symbol is linked and the symbol is not
+defined, the weak symbol becomes an alias for some other symbol. There
+are three variants of weak externals:
+@itemize
+@item Definition is searched for in objects and libraries, historically
+called lazy externals.
+@item Definition is searched for only in other objects, not in libraries.
+This form is not presently implemented.
+@item No search; the symbol is an alias. This form is not presently
+implemented.
+@end itemize
+As a GNU extension, weak symbols that do not specify an alternate symbol
+are supported. If the symbol is undefined when linking, the symbol
+uses a default value.
+@end table
+
+@ifclear GENERIC
+@lowersections
+@end ifclear
+@end ifset
+
+@ifset XTENSA
+@ifclear GENERIC
+@raisesections
+@end ifclear
+
+@node Xtensa
+@section @code{ld} and Xtensa Processors
+
+@cindex Xtensa processors
+The default @command{ld} behavior for Xtensa processors is to interpret
+@code{SECTIONS} commands so that lists of explicitly named sections in a
+specification with a wildcard file will be interleaved when necessary to
+keep literal pools within the range of PC-relative load offsets. For
+example, with the command:
+
+@smallexample
+SECTIONS
+@{
+ .text : @{
+ *(.literal .text)
+ @}
+@}
+@end smallexample
+
+@noindent
+@command{ld} may interleave some of the @code{.literal}
+and @code{.text} sections from different object files to ensure that the
+literal pools are within the range of PC-relative load offsets. A valid
+interleaving might place the @code{.literal} sections from an initial
+group of files followed by the @code{.text} sections of that group of
+files. Then, the @code{.literal} sections from the rest of the files
+and the @code{.text} sections from the rest of the files would follow.
+
+@cindex @option{--relax} on Xtensa
+@cindex relaxing on Xtensa
+Relaxation is enabled by default for the Xtensa version of @command{ld} and
+provides two important link-time optimizations. The first optimization
+is to combine identical literal values to reduce code size. A redundant
+literal will be removed and all the @code{L32R} instructions that use it
+will be changed to reference an identical literal, as long as the
+location of the replacement literal is within the offset range of all
+the @code{L32R} instructions. The second optimization is to remove
+unnecessary overhead from assembler-generated ``longcall'' sequences of
+@code{L32R}/@code{CALLX@var{n}} when the target functions are within
+range of direct @code{CALL@var{n}} instructions.
+
+For each of these cases where an indirect call sequence can be optimized
+to a direct call, the linker will change the @code{CALLX@var{n}}
+instruction to a @code{CALL@var{n}} instruction, remove the @code{L32R}
+instruction, and remove the literal referenced by the @code{L32R}
+instruction if it is not used for anything else. Removing the
+@code{L32R} instruction always reduces code size but can potentially
+hurt performance by changing the alignment of subsequent branch targets.
+By default, the linker will always preserve alignments, either by
+switching some instructions between 24-bit encodings and the equivalent
+density instructions or by inserting a no-op in place of the @code{L32R}
+instruction that was removed. If code size is more important than
+performance, the @option{--size-opt} option can be used to prevent the
+linker from widening density instructions or inserting no-ops, except in
+a few cases where no-ops are required for correctness.
+
+The following Xtensa-specific command-line options can be used to
+control the linker:
+
+@cindex Xtensa options
+@table @option
+@kindex --no-relax
+@item --no-relax
+Since the Xtensa version of @code{ld} enables the @option{--relax} option
+by default, the @option{--no-relax} option is provided to disable
+relaxation.
+
+@item --size-opt
+When optimizing indirect calls to direct calls, optimize for code size
+more than performance. With this option, the linker will not insert
+no-ops or widen density instructions to preserve branch target
+alignment. There may still be some cases where no-ops are required to
+preserve the correctness of the code.
+@end table
+