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 struct expression;
  93 struct agent_expr;
  94 struct axs_value;
  95 struct type;
  96 struct ui_file;
  97
  98 namespace expr
  99 {
 100
 101 class operation;
 102 typedef std::unique_ptr<operation> operation_up;
 103
 104 /* Base class for an operation.  An operation is a single component of
 105    an expression.  */
 106
 107 class operation
 108 {
 109 protected:
 110
 111   operation () = default;
 112   DISABLE_COPY_AND_ASSIGN (operation);
 113
 114 public:
 115
 116   virtual ~operation () = default;
 117
 118   /* Evaluate this operation.  */
 119   virtual value *evaluate (struct type *expect_type,
 120                            struct expression *exp,
 121                            enum noside noside) = 0;
 122
 123   /* Evaluate this operation in a context where C-like coercion is
 124      needed.  */
 125   virtual value *evaluate_with_coercion (struct expression *exp,
 126                                          enum noside noside)
 127   {
 128     return evaluate (nullptr, exp, noside);
 129   }
 130
 131   /* Evaluate this expression in the context of a cast to
 132      EXPECT_TYPE.  */
 133   virtual value *evaluate_for_cast (struct type *expect_type,
 134                                     struct expression *exp,
 135                                     enum noside noside);
 136
 137   /* Evaluate this expression in the context of a sizeof
 138      operation.  */
 139   virtual value *evaluate_for_sizeof (struct expression *exp,
 140                                       enum noside noside);
 141
 142   /* Evaluate this expression in the context of an address-of
 143      operation.  Must return the address.  */
 144   virtual value *evaluate_for_address (struct expression *exp,
 145                                        enum noside noside);
 146
 147   /* True if this is a constant expression.  */
 148   virtual bool constant_p () const
 149   { return false; }
 150
 151   /* Return true if this operation uses OBJFILE (and will become
 152      dangling when OBJFILE is unloaded), otherwise return false.
 153      OBJFILE must not be a separate debug info file.  */
 154   virtual bool uses_objfile (struct objfile *objfile) const
 155   { return false; }
 156
 157   /* Generate agent expression bytecodes for this operation.  */
 158   void generate_ax (struct expression *exp, struct agent_expr *ax,
 159                     struct axs_value *value,
 160                     struct type *cast_type = nullptr);
 161
 162   /* Return the opcode that is implemented by this operation.  */
 163   virtual enum exp_opcode opcode () const = 0;
 164
 165   /* Print this operation to STREAM.  */
 166   virtual void dump (struct ui_file *stream, int depth) const = 0;
 167
 168   /* Call to indicate that this is the outermost operation in the
 169      expression.  This should almost never be overridden.  */
 170   virtual void set_outermost () { }
 171
 172 protected:
 173
 174   /* Called by generate_ax to do the work for this particular
 175      operation.  */
 176   virtual void do_generate_ax (struct expression *exp,
 177                                struct agent_expr *ax,
 178                                struct axs_value *value,
 179                                struct type *cast_type)
 180   {
 181     error (_("Cannot translate to agent expression"));
 182   }
 183 };
 184
 185 /* A helper function for creating an operation_up, given a type.  */
 186 template<typename T, typename... Arg>
 187 operation_up
 188 make_operation (Arg... args)
 189 {
 190   return operation_up (new T (std::forward<Arg> (args)...));
 191 }
 192
 193 }
 194
 195 union exp_element
 196   {
 197     enum exp_opcode opcode;
 198     struct symbol *symbol;
 199     struct minimal_symbol *msymbol;
 200     LONGEST longconst;
 201     gdb_byte floatconst[16];
 202     /* Really sizeof (union exp_element) characters (or less for the last
 203        element of a string).  */
 204     char string;
 205     struct type *type;
 206     struct internalvar *internalvar;
 207     const struct block *block;
 208     struct objfile *objfile;
 209   };
 210
 211 struct expression
 212 {
 213   expression (const struct language_defn *, struct gdbarch *, size_t);
 214   ~expression ();
 215   DISABLE_COPY_AND_ASSIGN (expression);
 216
 217   void resize (size_t);
 218
 219   /* Return the opcode for the outermost sub-expression of this
 220      expression.  */
 221   enum exp_opcode first_opcode () const
 222   {
 223       return elts[0].opcode;
 224   }
 225
 226   /* Evaluate the expression.  EXPECT_TYPE is the context type of the
 227      expression; normally this should be nullptr.  NOSIDE controls how
 228      evaluation is performed.  */
 229   struct value *evaluate (struct type *expect_type, enum noside noside);
 230
 231   /* Language it was entered in.  */
 232   const struct language_defn *language_defn;
 233   /* Architecture it was parsed in.  */
 234   struct gdbarch *gdbarch;
 235   int nelts = 0;
 236   union exp_element *elts;
 237 };
 238
 239 typedef std::unique_ptr<expression> expression_up;
 240
 241 /* Macros for converting between number of expression elements and bytes
 242    to store that many expression elements.  */
 243
 244 #define EXP_ELEM_TO_BYTES(elements) \
 245     ((elements) * sizeof (union exp_element))
 246 #define BYTES_TO_EXP_ELEM(bytes) \
 247     (((bytes) + sizeof (union exp_element) - 1) / sizeof (union exp_element))
 248
 249 /* From parse.c */
 250
 251 class innermost_block_tracker;
 252 extern expression_up parse_expression (const char *,
 253                                        innermost_block_tracker * = nullptr,
 254                                        bool void_context_p = false);
 255
 256 extern expression_up parse_expression_with_language (const char *string,
 257                                                      enum language lang);
 258
 259 extern struct type *parse_expression_for_completion
 260     (const char *, gdb::unique_xmalloc_ptr<char> *, enum type_code *);
 261
 262 class innermost_block_tracker;
 263 extern expression_up parse_exp_1 (const char **, CORE_ADDR pc,
 264                                   const struct block *, int,
 265                                   innermost_block_tracker * = nullptr);
 266
 267 /* From eval.c */
 268
 269 extern struct value *evaluate_subexp_standard
 270   (struct type *, struct expression *, int *, enum noside);
 271
 272 /* Evaluate a function call.  The function to be called is in CALLEE and
 273    the arguments passed to the function are in ARGVEC.
 274    FUNCTION_NAME is the name of the function, if known.
 275    DEFAULT_RETURN_TYPE is used as the function's return type if the return
 276    type is unknown.  */
 277
 278 extern struct value *evaluate_subexp_do_call (expression *exp,
 279                                               enum noside noside,
 280                                               value *callee,
 281                                               gdb::array_view<value *> argvec,
 282                                               const char *function_name,
 283                                               type *default_return_type);
 284
 285 /* From expprint.c */
 286
 287 extern void print_expression (struct expression *, struct ui_file *);
 288
 289 extern const char *op_name (enum exp_opcode opcode);
 290
 291 extern const char *op_string (enum exp_opcode);
 292
 293 extern void dump_raw_expression (struct expression *,
 294                                  struct ui_file *, const char *);
 295 extern void dump_prefix_expression (struct expression *, struct ui_file *);
 296
 297 /* In an OP_RANGE expression, either bound could be empty, indicating
 298    that its value is by default that of the corresponding bound of the
 299    array or string.  Also, the upper end of the range can be exclusive
 300    or inclusive.  So we have six sorts of subrange.  This enumeration
 301    type is to identify this.  */
 302
 303 enum range_flag : unsigned
 304 {
 305   /* This is a standard range.  Both the lower and upper bounds are
 306      defined, and the bounds are inclusive.  */
 307   RANGE_STANDARD = 0,
 308
 309   /* The low bound was not given.  */
 310   RANGE_LOW_BOUND_DEFAULT = 1 << 0,
 311
 312   /* The high bound was not given.  */
 313   RANGE_HIGH_BOUND_DEFAULT = 1 << 1,
 314
 315   /* The high bound of this range is exclusive.  */
 316   RANGE_HIGH_BOUND_EXCLUSIVE = 1 << 2,
 317
 318   /* The range has a stride.  */
 319   RANGE_HAS_STRIDE = 1 << 3,
 320 };
 321
 322 DEF_ENUM_FLAGS_TYPE (enum range_flag, range_flags);
 323
 324 #endif /* !defined (EXPRESSION_H) */