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 enum exp_opcode : uint8_t
  44   {
  45 #define OP(name) name ,
  46
  47 #include "std-operator.def"
  48
  49 #undef OP
  50   };
  51
  52 /* Values of NOSIDE argument to eval_subexp.  */
  53
  54 enum noside
  55   {
  56     EVAL_NORMAL,
  57     EVAL_AVOID_SIDE_EFFECTS     /* Don't modify any variables or
  58                                    call any functions.  The value
  59                                    returned will have the correct
  60                                    type, and will have an
  61                                    approximately correct lvalue
  62                                    type (inaccuracy: anything that is
  63                                    listed as being in a register in
  64                                    the function in which it was
  65                                    declared will be lval_register).
  66                                    Ideally this would not even read
  67                                    target memory, but currently it
  68                                    does in many situations.  */
  69   };
  70
  71 struct expression;
  72 struct agent_expr;
  73 struct axs_value;
  74 struct type;
  75 struct ui_file;
  76
  77 namespace expr
  78 {
  79
  80 class operation;
  81 typedef std::unique_ptr<operation> operation_up;
  82
  83 /* Base class for an operation.  An operation is a single component of
  84    an expression.  */
  85
  86 class operation
  87 {
  88 protected:
  89
  90   operation () = default;
  91   DISABLE_COPY_AND_ASSIGN (operation);
  92
  93 public:
  94
  95   virtual ~operation () = default;
  96
  97   /* Evaluate this operation.  */
  98   virtual value *evaluate (struct type *expect_type,
  99                            struct expression *exp,
 100                            enum noside noside) = 0;
 101
 102   /* Evaluate this operation in a context where C-like coercion is
 103      needed.  */
 104   virtual value *evaluate_with_coercion (struct expression *exp,
 105                                          enum noside noside)
 106   {
 107     return evaluate (nullptr, exp, noside);
 108   }
 109
 110   /* Evaluate this expression in the context of a cast to
 111      EXPECT_TYPE.  */
 112   virtual value *evaluate_for_cast (struct type *expect_type,
 113                                     struct expression *exp,
 114                                     enum noside noside);
 115
 116   /* Evaluate this expression in the context of a sizeof
 117      operation.  */
 118   virtual value *evaluate_for_sizeof (struct expression *exp,
 119                                       enum noside noside);
 120
 121   /* Evaluate this expression in the context of an address-of
 122      operation.  Must return the address.  */
 123   virtual value *evaluate_for_address (struct expression *exp,
 124                                        enum noside noside);
 125
 126   /* Evaluate a function call, with this object as the callee.
 127      EXPECT_TYPE, EXP, and NOSIDE have the same meaning as in
 128      'evaluate'.  ARGS holds the operations that should be evaluated
 129      to get the arguments to the call.  */
 130   virtual value *evaluate_funcall (struct type *expect_type,
 131                                    struct expression *exp,
 132                                    enum noside noside,
 133                                    const std::vector<operation_up> &args)
 134   {
 135     /* Defer to the helper overload.  */
 136     return evaluate_funcall (expect_type, exp, noside, nullptr, args);
 137   }
 138
 139   /* True if this is a constant expression.  */
 140   virtual bool constant_p () const
 141   { return false; }
 142
 143   /* Return true if this operation uses OBJFILE (and will become
 144      dangling when OBJFILE is unloaded), otherwise return false.
 145      OBJFILE must not be a separate debug info file.  */
 146   virtual bool uses_objfile (struct objfile *objfile) const
 147   { return false; }
 148
 149   /* Generate agent expression bytecodes for this operation.  */
 150   void generate_ax (struct expression *exp, struct agent_expr *ax,
 151                     struct axs_value *value,
 152                     struct type *cast_type = nullptr);
 153
 154   /* Return the opcode that is implemented by this operation.  */
 155   virtual enum exp_opcode opcode () const = 0;
 156
 157   /* Print this operation to STREAM.  */
 158   virtual void dump (struct ui_file *stream, int depth) const = 0;
 159
 160   /* Call to indicate that this is the outermost operation in the
 161      expression.  This should almost never be overridden.  */
 162   virtual void set_outermost () { }
 163
 164 protected:
 165
 166   /* A helper overload that wraps evaluate_subexp_do_call.  */
 167   value *evaluate_funcall (struct type *expect_type,
 168                            struct expression *exp,
 169                            enum noside noside,
 170                            const char *function_name,
 171                            const std::vector<operation_up> &args);
 172
 173   /* Called by generate_ax to do the work for this particular
 174      operation.  */
 175   virtual void do_generate_ax (struct expression *exp,
 176                                struct agent_expr *ax,
 177                                struct axs_value *value,
 178                                struct type *cast_type)
 179   {
 180     error (_("Cannot translate to agent expression"));
 181   }
 182 };
 183
 184 /* A helper function for creating an operation_up, given a type.  */
 185 template<typename T, typename... Arg>
 186 operation_up
 187 make_operation (Arg... args)
 188 {
 189   return operation_up (new T (std::forward<Arg> (args)...));
 190 }
 191
 192 }
 193
 194 struct expression
 195 {
 196   expression (const struct language_defn *lang, struct gdbarch *arch)
 197     : language_defn (lang),
 198       gdbarch (arch)
 199   {
 200   }
 201
 202   DISABLE_COPY_AND_ASSIGN (expression);
 203
 204   /* Return the opcode for the outermost sub-expression of this
 205      expression.  */
 206   enum exp_opcode first_opcode () const
 207   {
 208     return op->opcode ();
 209   }
 210
 211   /* Evaluate the expression.  EXPECT_TYPE is the context type of the
 212      expression; normally this should be nullptr.  NOSIDE controls how
 213      evaluation is performed.  */
 214   struct value *evaluate (struct type *expect_type, enum noside noside);
 215
 216   /* Language it was entered in.  */
 217   const struct language_defn *language_defn;
 218   /* Architecture it was parsed in.  */
 219   struct gdbarch *gdbarch;
 220   expr::operation_up op;
 221 };
 222
 223 typedef std::unique_ptr<expression> expression_up;
 224
 225 /* From parse.c */
 226
 227 class innermost_block_tracker;
 228 extern expression_up parse_expression (const char *,
 229                                        innermost_block_tracker * = nullptr,
 230                                        bool void_context_p = false);
 231
 232 extern expression_up parse_expression_with_language (const char *string,
 233                                                      enum language lang);
 234
 235 extern struct type *parse_expression_for_completion
 236     (const char *, gdb::unique_xmalloc_ptr<char> *, enum type_code *);
 237
 238 class innermost_block_tracker;
 239 extern expression_up parse_exp_1 (const char **, CORE_ADDR pc,
 240                                   const struct block *, int,
 241                                   innermost_block_tracker * = nullptr);
 242
 243 /* From eval.c */
 244
 245 /* Evaluate a function call.  The function to be called is in CALLEE and
 246    the arguments passed to the function are in ARGVEC.
 247    FUNCTION_NAME is the name of the function, if known.
 248    DEFAULT_RETURN_TYPE is used as the function's return type if the return
 249    type is unknown.  */
 250
 251 extern struct value *evaluate_subexp_do_call (expression *exp,
 252                                               enum noside noside,
 253                                               value *callee,
 254                                               gdb::array_view<value *> argvec,
 255                                               const char *function_name,
 256                                               type *default_return_type);
 257
 258 /* From expprint.c */
 259
 260 extern const char *op_name (enum exp_opcode opcode);
 261
 262 extern void dump_prefix_expression (struct expression *, struct ui_file *);
 263
 264 /* In an OP_RANGE expression, either bound could be empty, indicating
 265    that its value is by default that of the corresponding bound of the
 266    array or string.  Also, the upper end of the range can be exclusive
 267    or inclusive.  So we have six sorts of subrange.  This enumeration
 268    type is to identify this.  */
 269
 270 enum range_flag : unsigned
 271 {
 272   /* This is a standard range.  Both the lower and upper bounds are
 273      defined, and the bounds are inclusive.  */
 274   RANGE_STANDARD = 0,
 275
 276   /* The low bound was not given.  */
 277   RANGE_LOW_BOUND_DEFAULT = 1 << 0,
 278
 279   /* The high bound was not given.  */
 280   RANGE_HIGH_BOUND_DEFAULT = 1 << 1,
 281
 282   /* The high bound of this range is exclusive.  */
 283   RANGE_HIGH_BOUND_EXCLUSIVE = 1 << 2,
 284
 285   /* The range has a stride.  */
 286   RANGE_HAS_STRIDE = 1 << 3,
 287 };
 288
 289 DEF_ENUM_FLAGS_TYPE (enum range_flag, range_flags);
 290
 291 #endif /* !defined (EXPRESSION_H) */