gdb/expression.h

   1 /* Definitions for expressions stored in reversed prefix form, for GDB.
   2
   3    Copyright (C) 1986-2021 Free Software Foundation, Inc.
   4
   5    This file is part of GDB.
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  19
  20 #if !defined (EXPRESSION_H)
  21 #define EXPRESSION_H 1
  22
  23 #include "gdbtypes.h"
  24
  25 /* While parsing expressions we need to track the innermost lexical block
  26    that we encounter.  In some situations we need to track the innermost
  27    block just for symbols, and in other situations we want to track the
  28    innermost block for symbols and registers.  These flags are used by the
  29    innermost block tracker to control which blocks we consider for the
  30    innermost block.  These flags can be combined together as needed.  */
  31
  32 enum innermost_block_tracker_type
  33 {
  34   /* Track the innermost block for symbols within an expression.  */
  35   INNERMOST_BLOCK_FOR_SYMBOLS = (1 << 0),
  36
  37   /* Track the innermost block for registers within an expression.  */
  38   INNERMOST_BLOCK_FOR_REGISTERS = (1 << 1)
  39 };
  40 DEF_ENUM_FLAGS_TYPE (enum innermost_block_tracker_type,
  41                      innermost_block_tracker_types);
  42
  43 /* Definitions for saved C expressions.  */
  44
  45 /* An expression is represented as a vector of union exp_element's.
  46    Each exp_element is an opcode, except that some opcodes cause
  47    the following exp_element to be treated as a long or double constant
  48    or as a variable.  The opcodes are obeyed, using a stack for temporaries.
  49    The value is left on the temporary stack at the end.  */
  50
  51 /* When it is necessary to include a string,
  52    it can occupy as many exp_elements as it needs.
  53    We find the length of the string using strlen,
  54    divide to find out how many exp_elements are used up,
  55    and skip that many.  Strings, like numbers, are indicated
  56    by the preceding opcode.  */
  57
  58 enum exp_opcode : uint8_t
  59   {
  60 #define OP(name) name ,
  61
  62 #include "std-operator.def"
  63
  64 #undef OP
  65
  66     /* Existing only to swallow the last comma (',') from last .inc file.  */
  67     OP_UNUSED_LAST
  68   };
  69
  70 /* Values of NOSIDE argument to eval_subexp.  */
  71
  72 enum noside
  73   {
  74     EVAL_NORMAL,
  75     EVAL_SKIP,                  /* Only effect is to increment pos.
  76                                    Return type information where
  77                                    possible.  */
  78     EVAL_AVOID_SIDE_EFFECTS     /* Don't modify any variables or
  79                                    call any functions.  The value
  80                                    returned will have the correct
  81                                    type, and will have an
  82                                    approximately correct lvalue
  83                                    type (inaccuracy: anything that is
  84                                    listed as being in a register in
  85                                    the function in which it was
  86                                    declared will be lval_register).
  87                                    Ideally this would not even read
  88                                    target memory, but currently it
  89                                    does in many situations.  */
  90   };
  91
  92 union exp_element
  93   {
  94     enum exp_opcode opcode;
  95     struct symbol *symbol;
  96     struct minimal_symbol *msymbol;
  97     LONGEST longconst;
  98     gdb_byte floatconst[16];
  99     /* Really sizeof (union exp_element) characters (or less for the last
 100        element of a string).  */
 101     char string;
 102     struct type *type;
 103     struct internalvar *internalvar;
 104     const struct block *block;
 105     struct objfile *objfile;
 106   };
 107
 108 struct expression
 109 {
 110   expression (const struct language_defn *, struct gdbarch *, size_t);
 111   ~expression ();
 112   DISABLE_COPY_AND_ASSIGN (expression);
 113
 114   void resize (size_t);
 115
 116   /* Return the opcode for the outermost sub-expression of this
 117      expression.  */
 118   enum exp_opcode first_opcode () const
 119   {
 120       return elts[0].opcode;
 121   }
 122
 123   /* Evaluate the expression.  EXPECT_TYPE is the context type of the
 124      expression; normally this should be nullptr.  NOSIDE controls how
 125      evaluation is performed.  */
 126   struct value *evaluate (struct type *expect_type, enum noside noside);
 127
 128   /* Language it was entered in.  */
 129   const struct language_defn *language_defn;
 130   /* Architecture it was parsed in.  */
 131   struct gdbarch *gdbarch;
 132   int nelts = 0;
 133   union exp_element *elts;
 134 };
 135
 136 typedef std::unique_ptr<expression> expression_up;
 137
 138 /* Macros for converting between number of expression elements and bytes
 139    to store that many expression elements.  */
 140
 141 #define EXP_ELEM_TO_BYTES(elements) \
 142     ((elements) * sizeof (union exp_element))
 143 #define BYTES_TO_EXP_ELEM(bytes) \
 144     (((bytes) + sizeof (union exp_element) - 1) / sizeof (union exp_element))
 145
 146 /* From parse.c */
 147
 148 class innermost_block_tracker;
 149 extern expression_up parse_expression (const char *,
 150                                        innermost_block_tracker * = nullptr,
 151                                        bool void_context_p = false);
 152
 153 extern expression_up parse_expression_with_language (const char *string,
 154                                                      enum language lang);
 155
 156 extern struct type *parse_expression_for_completion
 157     (const char *, gdb::unique_xmalloc_ptr<char> *, enum type_code *);
 158
 159 class innermost_block_tracker;
 160 extern expression_up parse_exp_1 (const char **, CORE_ADDR pc,
 161                                   const struct block *, int,
 162                                   innermost_block_tracker * = nullptr);
 163
 164 /* From eval.c */
 165
 166 extern struct value *evaluate_subexp_standard
 167   (struct type *, struct expression *, int *, enum noside);
 168
 169 /* Evaluate a function call.  The function to be called is in CALLEE and
 170    the arguments passed to the function are in ARGVEC.
 171    FUNCTION_NAME is the name of the function, if known.
 172    DEFAULT_RETURN_TYPE is used as the function's return type if the return
 173    type is unknown.  */
 174
 175 extern struct value *evaluate_subexp_do_call (expression *exp,
 176                                               enum noside noside,
 177                                               value *callee,
 178                                               gdb::array_view<value *> argvec,
 179                                               const char *function_name,
 180                                               type *default_return_type);
 181
 182 /* From expprint.c */
 183
 184 extern void print_expression (struct expression *, struct ui_file *);
 185
 186 extern const char *op_name (enum exp_opcode opcode);
 187
 188 extern const char *op_string (enum exp_opcode);
 189
 190 extern void dump_raw_expression (struct expression *,
 191                                  struct ui_file *, const char *);
 192 extern void dump_prefix_expression (struct expression *, struct ui_file *);
 193
 194 /* In an OP_RANGE expression, either bound could be empty, indicating
 195    that its value is by default that of the corresponding bound of the
 196    array or string.  Also, the upper end of the range can be exclusive
 197    or inclusive.  So we have six sorts of subrange.  This enumeration
 198    type is to identify this.  */
 199
 200 enum range_flag : unsigned
 201 {
 202   /* This is a standard range.  Both the lower and upper bounds are
 203      defined, and the bounds are inclusive.  */
 204   RANGE_STANDARD = 0,
 205
 206   /* The low bound was not given.  */
 207   RANGE_LOW_BOUND_DEFAULT = 1 << 0,
 208
 209   /* The high bound was not given.  */
 210   RANGE_HIGH_BOUND_DEFAULT = 1 << 1,
 211
 212   /* The high bound of this range is exclusive.  */
 213   RANGE_HIGH_BOUND_EXCLUSIVE = 1 << 2,
 214
 215   /* The range has a stride.  */
 216   RANGE_HAS_STRIDE = 1 << 3,
 217 };
 218
 219 DEF_ENUM_FLAGS_TYPE (enum range_flag, range_flags);
 220
 221 #endif /* !defined (EXPRESSION_H) */