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/* Definitions for expressions stored in reversed prefix form, for GDB.
Copyright (C) 1986-2021 Free Software Foundation, Inc.
This file is part of GDB.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <>. */
#if !defined (EXPRESSION_H)
#define EXPRESSION_H 1
#include "gdbtypes.h"
/* While parsing expressions we need to track the innermost lexical block
that we encounter. In some situations we need to track the innermost
block just for symbols, and in other situations we want to track the
innermost block for symbols and registers. These flags are used by the
innermost block tracker to control which blocks we consider for the
innermost block. These flags can be combined together as needed. */
enum innermost_block_tracker_type
/* Track the innermost block for symbols within an expression. */
/* Track the innermost block for registers within an expression. */
DEF_ENUM_FLAGS_TYPE (enum innermost_block_tracker_type,
enum exp_opcode : uint8_t
#define OP(name) name ,
#include "std-operator.def"
#undef OP
/* Values of NOSIDE argument to eval_subexp. */
enum noside
EVAL_AVOID_SIDE_EFFECTS /* Don't modify any variables or
call any functions. The value
returned will have the correct
type, and will have an
approximately correct lvalue
type (inaccuracy: anything that is
listed as being in a register in
the function in which it was
declared will be lval_register).
Ideally this would not even read
target memory, but currently it
does in many situations. */
struct expression;
struct agent_expr;
struct axs_value;
struct type;
struct ui_file;
namespace expr
class operation;
typedef std::unique_ptr<operation> operation_up;
/* Base class for an operation. An operation is a single component of
an expression. */
class operation
operation () = default;
virtual ~operation () = default;
/* Evaluate this operation. */
virtual value *evaluate (struct type *expect_type,
struct expression *exp,
enum noside noside) = 0;
/* Evaluate this operation in a context where C-like coercion is
needed. */
virtual value *evaluate_with_coercion (struct expression *exp,
enum noside noside)
return evaluate (nullptr, exp, noside);
/* Evaluate this expression in the context of a cast to
virtual value *evaluate_for_cast (struct type *expect_type,
struct expression *exp,
enum noside noside);
/* Evaluate this expression in the context of a sizeof
operation. */
virtual value *evaluate_for_sizeof (struct expression *exp,
enum noside noside);
/* Evaluate this expression in the context of an address-of
operation. Must return the address. */
virtual value *evaluate_for_address (struct expression *exp,
enum noside noside);
/* Evaluate a function call, with this object as the callee.
EXPECT_TYPE, EXP, and NOSIDE have the same meaning as in
'evaluate'. ARGS holds the operations that should be evaluated
to get the arguments to the call. */
virtual value *evaluate_funcall (struct type *expect_type,
struct expression *exp,
enum noside noside,
const std::vector<operation_up> &args)
/* Defer to the helper overload. */
return evaluate_funcall (expect_type, exp, noside, nullptr, args);
/* True if this is a constant expression. */
virtual bool constant_p () const
{ return false; }
/* Return true if this operation uses OBJFILE (and will become
dangling when OBJFILE is unloaded), otherwise return false.
OBJFILE must not be a separate debug info file. */
virtual bool uses_objfile (struct objfile *objfile) const
{ return false; }
/* Generate agent expression bytecodes for this operation. */
void generate_ax (struct expression *exp, struct agent_expr *ax,
struct axs_value *value,
struct type *cast_type = nullptr);
/* Return the opcode that is implemented by this operation. */
virtual enum exp_opcode opcode () const = 0;
/* Print this operation to STREAM. */
virtual void dump (struct ui_file *stream, int depth) const = 0;
/* Call to indicate that this is the outermost operation in the
expression. This should almost never be overridden. */
virtual void set_outermost () { }
/* A helper overload that wraps evaluate_subexp_do_call. */
value *evaluate_funcall (struct type *expect_type,
struct expression *exp,
enum noside noside,
const char *function_name,
const std::vector<operation_up> &args);
/* Called by generate_ax to do the work for this particular
operation. */
virtual void do_generate_ax (struct expression *exp,
struct agent_expr *ax,
struct axs_value *value,
struct type *cast_type)
error (_("Cannot translate to agent expression"));
/* A helper function for creating an operation_up, given a type. */
template<typename T, typename... Arg>
make_operation (Arg... args)
return operation_up (new T (std::forward<Arg> (args)...));
struct expression
expression (const struct language_defn *lang, struct gdbarch *arch)
: language_defn (lang),
gdbarch (arch)
/* Return the opcode for the outermost sub-expression of this
expression. */
enum exp_opcode first_opcode () const
return op->opcode ();
/* Evaluate the expression. EXPECT_TYPE is the context type of the
expression; normally this should be nullptr. NOSIDE controls how
evaluation is performed. */
struct value *evaluate (struct type *expect_type, enum noside noside);
/* Language it was entered in. */
const struct language_defn *language_defn;
/* Architecture it was parsed in. */
struct gdbarch *gdbarch;
expr::operation_up op;
typedef std::unique_ptr<expression> expression_up;
/* From parse.c */
class innermost_block_tracker;
extern expression_up parse_expression (const char *,
innermost_block_tracker * = nullptr,
bool void_context_p = false);
extern expression_up parse_expression_with_language (const char *string,
enum language lang);
extern struct type *parse_expression_for_completion
(const char *, gdb::unique_xmalloc_ptr<char> *, enum type_code *);
class innermost_block_tracker;
extern expression_up parse_exp_1 (const char **, CORE_ADDR pc,
const struct block *, int,
innermost_block_tracker * = nullptr);
/* From eval.c */
/* Evaluate a function call. The function to be called is in CALLEE and
the arguments passed to the function are in ARGVEC.
FUNCTION_NAME is the name of the function, if known.
DEFAULT_RETURN_TYPE is used as the function's return type if the return
type is unknown. */
extern struct value *evaluate_subexp_do_call (expression *exp,
enum noside noside,
value *callee,
gdb::array_view<value *> argvec,
const char *function_name,
type *default_return_type);
/* From expprint.c */
extern const char *op_name (enum exp_opcode opcode);
extern void dump_prefix_expression (struct expression *, struct ui_file *);
/* In an OP_RANGE expression, either bound could be empty, indicating
that its value is by default that of the corresponding bound of the
array or string. Also, the upper end of the range can be exclusive
or inclusive. So we have six sorts of subrange. This enumeration
type is to identify this. */
enum range_flag : unsigned
/* This is a standard range. Both the lower and upper bounds are
defined, and the bounds are inclusive. */
/* The low bound was not given. */
/* The high bound was not given. */
/* The high bound of this range is exclusive. */
/* The range has a stride. */
DEF_ENUM_FLAGS_TYPE (enum range_flag, range_flags);
#endif /* !defined (EXPRESSION_H) */