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   /* Evaluate a function call, with this object as the callee.
 148      EXPECT_TYPE, EXP, and NOSIDE have the same meaning as in
 149      'evaluate'.  ARGS holds the operations that should be evaluated
 150      to get the arguments to the call.  */
 151   virtual value *evaluate_funcall (struct type *expect_type,
 152                                    struct expression *exp,
 153                                    enum noside noside,
 154                                    const std::vector<operation_up> &args)
 155   {
 156     /* Defer to the helper overload.  */
 157     return evaluate_funcall (expect_type, exp, noside, nullptr, args);
 158   }
 159
 160   /* True if this is a constant expression.  */
 161   virtual bool constant_p () const
 162   { return false; }
 163
 164   /* Return true if this operation uses OBJFILE (and will become
 165      dangling when OBJFILE is unloaded), otherwise return false.
 166      OBJFILE must not be a separate debug info file.  */
 167   virtual bool uses_objfile (struct objfile *objfile) const
 168   { return false; }
 169
 170   /* Generate agent expression bytecodes for this operation.  */
 171   void generate_ax (struct expression *exp, struct agent_expr *ax,
 172                     struct axs_value *value,
 173                     struct type *cast_type = nullptr);
 174
 175   /* Return the opcode that is implemented by this operation.  */
 176   virtual enum exp_opcode opcode () const = 0;
 177
 178   /* Print this operation to STREAM.  */
 179   virtual void dump (struct ui_file *stream, int depth) const = 0;
 180
 181   /* Call to indicate that this is the outermost operation in the
 182      expression.  This should almost never be overridden.  */
 183   virtual void set_outermost () { }
 184
 185 protected:
 186
 187   /* A helper overload that wraps evaluate_subexp_do_call.  */
 188   value *evaluate_funcall (struct type *expect_type,
 189                            struct expression *exp,
 190                            enum noside noside,
 191                            const char *function_name,
 192                            const std::vector<operation_up> &args);
 193
 194   /* Called by generate_ax to do the work for this particular
 195      operation.  */
 196   virtual void do_generate_ax (struct expression *exp,
 197                                struct agent_expr *ax,
 198                                struct axs_value *value,
 199                                struct type *cast_type)
 200   {
 201     error (_("Cannot translate to agent expression"));
 202   }
 203 };
 204
 205 /* A helper function for creating an operation_up, given a type.  */
 206 template<typename T, typename... Arg>
 207 operation_up
 208 make_operation (Arg... args)
 209 {
 210   return operation_up (new T (std::forward<Arg> (args)...));
 211 }
 212
 213 }
 214
 215 union exp_element
 216   {
 217     enum exp_opcode opcode;
 218     struct symbol *symbol;
 219     struct minimal_symbol *msymbol;
 220     LONGEST longconst;
 221     gdb_byte floatconst[16];
 222     /* Really sizeof (union exp_element) characters (or less for the last
 223        element of a string).  */
 224     char string;
 225     struct type *type;
 226     struct internalvar *internalvar;
 227     const struct block *block;
 228     struct objfile *objfile;
 229   };
 230
 231 struct expression
 232 {
 233   expression (const struct language_defn *, struct gdbarch *, size_t);
 234   ~expression ();
 235   DISABLE_COPY_AND_ASSIGN (expression);
 236
 237   void resize (size_t);
 238
 239   /* Return the opcode for the outermost sub-expression of this
 240      expression.  */
 241   enum exp_opcode first_opcode () const
 242   {
 243     if (op != nullptr)
 244       return op->opcode ();
 245     return elts[0].opcode;
 246   }
 247
 248   /* Evaluate the expression.  EXPECT_TYPE is the context type of the
 249      expression; normally this should be nullptr.  NOSIDE controls how
 250      evaluation is performed.  */
 251   struct value *evaluate (struct type *expect_type, enum noside noside);
 252
 253   /* Language it was entered in.  */
 254   const struct language_defn *language_defn;
 255   /* Architecture it was parsed in.  */
 256   struct gdbarch *gdbarch;
 257   expr::operation_up op;
 258   int nelts = 0;
 259   union exp_element *elts;
 260 };
 261
 262 typedef std::unique_ptr<expression> expression_up;
 263
 264 /* Macros for converting between number of expression elements and bytes
 265    to store that many expression elements.  */
 266
 267 #define EXP_ELEM_TO_BYTES(elements) \
 268     ((elements) * sizeof (union exp_element))
 269 #define BYTES_TO_EXP_ELEM(bytes) \
 270     (((bytes) + sizeof (union exp_element) - 1) / sizeof (union exp_element))
 271
 272 /* From parse.c */
 273
 274 class innermost_block_tracker;
 275 extern expression_up parse_expression (const char *,
 276                                        innermost_block_tracker * = nullptr,
 277                                        bool void_context_p = false);
 278
 279 extern expression_up parse_expression_with_language (const char *string,
 280                                                      enum language lang);
 281
 282 extern struct type *parse_expression_for_completion
 283     (const char *, gdb::unique_xmalloc_ptr<char> *, enum type_code *);
 284
 285 class innermost_block_tracker;
 286 extern expression_up parse_exp_1 (const char **, CORE_ADDR pc,
 287                                   const struct block *, int,
 288                                   innermost_block_tracker * = nullptr);
 289
 290 /* From eval.c */
 291
 292 extern struct value *evaluate_subexp_standard
 293   (struct type *, struct expression *, int *, enum noside);
 294
 295 /* Evaluate a function call.  The function to be called is in CALLEE and
 296    the arguments passed to the function are in ARGVEC.
 297    FUNCTION_NAME is the name of the function, if known.
 298    DEFAULT_RETURN_TYPE is used as the function's return type if the return
 299    type is unknown.  */
 300
 301 extern struct value *evaluate_subexp_do_call (expression *exp,
 302                                               enum noside noside,
 303                                               value *callee,
 304                                               gdb::array_view<value *> argvec,
 305                                               const char *function_name,
 306                                               type *default_return_type);
 307
 308 /* From expprint.c */
 309
 310 extern void print_expression (struct expression *, struct ui_file *);
 311
 312 extern const char *op_name (enum exp_opcode opcode);
 313
 314 extern const char *op_string (enum exp_opcode);
 315
 316 extern void dump_raw_expression (struct expression *,
 317                                  struct ui_file *, const char *);
 318 extern void dump_prefix_expression (struct expression *, struct ui_file *);
 319
 320 /* In an OP_RANGE expression, either bound could be empty, indicating
 321    that its value is by default that of the corresponding bound of the
 322    array or string.  Also, the upper end of the range can be exclusive
 323    or inclusive.  So we have six sorts of subrange.  This enumeration
 324    type is to identify this.  */
 325
 326 enum range_flag : unsigned
 327 {
 328   /* This is a standard range.  Both the lower and upper bounds are
 329      defined, and the bounds are inclusive.  */
 330   RANGE_STANDARD = 0,
 331
 332   /* The low bound was not given.  */
 333   RANGE_LOW_BOUND_DEFAULT = 1 << 0,
 334
 335   /* The high bound was not given.  */
 336   RANGE_HIGH_BOUND_DEFAULT = 1 << 1,
 337
 338   /* The high bound of this range is exclusive.  */
 339   RANGE_HIGH_BOUND_EXCLUSIVE = 1 << 2,
 340
 341   /* The range has a stride.  */
 342   RANGE_HAS_STRIDE = 1 << 3,
 343 };
 344
 345 DEF_ENUM_FLAGS_TYPE (enum range_flag, range_flags);
 346
 347 #endif /* !defined (EXPRESSION_H) */