eval.c

早期freebsd实现

/* Evaluate expressions for GDB.
   Copyright 1986, 1987, 1989, 1991, 1992 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 2 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
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
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, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.  */

#include "defs.h"
#include "symtab.h"
#include "gdbtypes.h"
#include "value.h"
#include "expression.h"
#include "target.h"
#include "frame.h"

/* Values of NOSIDE argument to eval_subexp.  */
enum noside
{ EVAL_NORMAL,
  EVAL_SKIP,			/* Only effect is to increment pos.  */
  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).  */
};

/* Prototypes for local functions. */

static value
evaluate_subexp_for_sizeof PARAMS ((struct expression *, int *));

static value
evaluate_subexp_with_coercion PARAMS ((struct expression *, int *,
				       enum noside));

static value
evaluate_subexp_for_address PARAMS ((struct expression *, int *,
				     enum noside));

static value
evaluate_subexp PARAMS ((struct type *, struct expression *, int *,
			 enum noside));


/* Parse the string EXP as a C expression, evaluate it,
   and return the result as a number.  */

CORE_ADDR
parse_and_eval_address (exp)
     char *exp;
{
  struct expression *expr = parse_expression (exp);
  register CORE_ADDR addr;
  register struct cleanup *old_chain = 
      make_cleanup (free_current_contents, &expr);

  addr = value_as_pointer (evaluate_expression (expr));
  do_cleanups (old_chain);
  return addr;
}

/* Like parse_and_eval_address but takes a pointer to a char * variable
   and advanced that variable across the characters parsed.  */

CORE_ADDR
parse_and_eval_address_1 (expptr)
     char **expptr;
{
  struct expression *expr = parse_exp_1 (expptr, (struct block *)0, 0);
  register CORE_ADDR addr;
  register struct cleanup *old_chain =
      make_cleanup (free_current_contents, &expr);

  addr = value_as_pointer (evaluate_expression (expr));
  do_cleanups (old_chain);
  return addr;
}

value
parse_and_eval (exp)
     char *exp;
{
  struct expression *expr = parse_expression (exp);
  register value val;
  register struct cleanup *old_chain
    = make_cleanup (free_current_contents, &expr);

  val = evaluate_expression (expr);
  do_cleanups (old_chain);
  return val;
}

/* Parse up to a comma (or to a closeparen)
   in the string EXPP as an expression, evaluate it, and return the value.
   EXPP is advanced to point to the comma.  */

value
parse_to_comma_and_eval (expp)
     char **expp;
{
  struct expression *expr = parse_exp_1 (expp, (struct block *) 0, 1);
  register value val;
  register struct cleanup *old_chain
    = make_cleanup (free_current_contents, &expr);

  val = evaluate_expression (expr);
  do_cleanups (old_chain);
  return val;
}

/* Evaluate an expression in internal prefix form
   such as is constructed by parse.y.

   See expression.h for info on the format of an expression.  */

static value evaluate_subexp ();
static value evaluate_subexp_for_address ();
static value evaluate_subexp_for_sizeof ();
static value evaluate_subexp_with_coercion ();

/* return true if 'var' has an address in inferior's memory. */
static int
value_has_lval(var)
	register struct symbol *var;
{
  switch (SYMBOL_CLASS(var))
    {
    case LOC_STATIC:
    case LOC_LABEL:
    case LOC_ARG:
    case LOC_REF_ARG:
    case LOC_LOCAL:
    case LOC_BLOCK:
      return (1);
    }
  return (0);
}

value
evaluate_expression (exp)
     struct expression *exp;
{
  int pc = 0;
  return evaluate_subexp (NULL_TYPE, exp, &pc, EVAL_NORMAL);
}

/* Evaluate an expression, avoiding all memory references
   and getting a value whose type alone is correct.  */

value
evaluate_type (exp)
     struct expression *exp;
{
  int pc = 0;
  return evaluate_subexp (NULL_TYPE, exp, &pc, EVAL_AVOID_SIDE_EFFECTS);
}

static value
evaluate_subexp (expect_type, exp, pos, noside)
     struct type *expect_type;
     register struct expression *exp;
     register int *pos;
     enum noside noside;
{
  enum exp_opcode op;
  int tem;
  register int pc, pc2, oldpos;
  register value arg1, arg2, arg3;
  struct type *type;
  int nargs;
  value *argvec;

  pc = (*pos)++;
  op = exp->elts[pc].opcode;

  switch (op)
    {
    case OP_SCOPE:
      tem = strlen (&exp->elts[pc + 2].string);
      (*pos) += 3 + ((tem + sizeof (union exp_element))
		     / sizeof (union exp_element));
      arg1 = value_struct_elt_for_reference (exp->elts[pc + 1].type,
					     0,
					     exp->elts[pc + 1].type,
					     &exp->elts[pc + 2].string,
					     expect_type);
      if (arg1 == NULL)
	error ("There is no field named %s", &exp->elts[pc + 2].string);
      return arg1;

    case OP_LONG:
      (*pos) += 3;
      return value_from_longest (exp->elts[pc + 1].type,
			      exp->elts[pc + 2].longconst);

    case OP_DOUBLE:
      (*pos) += 3;
      return value_from_double (exp->elts[pc + 1].type,
				exp->elts[pc + 2].doubleconst);

    case OP_VAR_VALUE:
      (*pos) += 2;
      if (noside == EVAL_SKIP)
	goto nosideret;
      if (noside == EVAL_AVOID_SIDE_EFFECTS)
	{
	  struct symbol * sym = exp->elts[pc + 1].symbol;
	  enum lval_type lv;

	  switch (SYMBOL_CLASS (sym))
	    {
	    case LOC_CONST:
	    case LOC_LABEL:
	    case LOC_CONST_BYTES:
	      lv = not_lval;
	      break;

	    case LOC_REGISTER:
	    case LOC_REGPARM:
	      lv = lval_register;
	      break;

	    default:
	      lv = lval_memory;
	      break;
	    }

	  return value_zero (SYMBOL_TYPE (sym), lv);
	}
      else
	return value_of_variable (exp->elts[pc + 1].symbol);

    case OP_LAST:
      (*pos) += 2;
      return
	access_value_history (longest_to_int (exp->elts[pc + 1].longconst));

    case OP_REGISTER:
      (*pos) += 2;
      return value_of_register (longest_to_int (exp->elts[pc + 1].longconst));

    case OP_INTERNALVAR:
      (*pos) += 2;
      return value_of_internalvar (exp->elts[pc + 1].internalvar);

    case OP_STRING:
      tem = strlen (&exp->elts[pc + 1].string);
      (*pos) += 2 + ((tem + sizeof (union exp_element))
		     / sizeof (union exp_element));
      if (noside == EVAL_SKIP)
	goto nosideret;
      return value_string (&exp->elts[pc + 1].string, tem);

    case TERNOP_COND:
      /* Skip third and second args to evaluate the first one.  */
      arg1 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
      if (value_zerop (arg1))
	{
	  evaluate_subexp (NULL_TYPE, exp, pos, EVAL_SKIP);
	  return evaluate_subexp (NULL_TYPE, exp, pos, noside);
	}
      else
	{
	  arg2 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
	  evaluate_subexp (NULL_TYPE, exp, pos, EVAL_SKIP);
	  return arg2;
	}

    case OP_FUNCALL:
      (*pos) += 2;
      op = exp->elts[*pos].opcode;
      if (op == STRUCTOP_MEMBER || op == STRUCTOP_MPTR)
	{
	  int fnptr;

	  nargs = longest_to_int (exp->elts[pc + 1].longconst) + 1;
	  /* First, evaluate the structure into arg2 */
	  pc2 = (*pos)++;

	  if (noside == EVAL_SKIP)
	    goto nosideret;

	  if (op == STRUCTOP_MEMBER)
	    {
	      arg2 = evaluate_subexp_for_address (exp, pos, noside);
	    }
	  else
	    {
	      arg2 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
	    }

	  /* If the function is a virtual function, then the
	     aggregate value (providing the structure) plays
	     its part by providing the vtable.  Otherwise,
	     it is just along for the ride: call the function
	     directly.  */

	  arg1 = evaluate_subexp (NULL_TYPE, exp, pos, noside);

	  fnptr = longest_to_int (value_as_long (arg1));

	  if (METHOD_PTR_IS_VIRTUAL(fnptr))
	    {
	      int fnoffset = METHOD_PTR_TO_VOFFSET(fnptr);
	      struct type *basetype;
	      struct type *domain_type =
		  TYPE_DOMAIN_TYPE (TYPE_TARGET_TYPE (VALUE_TYPE (arg1)));
	      int i, j;
	      basetype = TYPE_TARGET_TYPE (VALUE_TYPE (arg2));
	      if (domain_type != basetype)
		  arg2 = value_cast(lookup_pointer_type (domain_type), arg2);
	      basetype = TYPE_VPTR_BASETYPE (domain_type);
	      for (i = TYPE_NFN_FIELDS (basetype) - 1; i >= 0; i--)
		{
		  struct fn_field *f = TYPE_FN_FIELDLIST1 (basetype, i);
		  /* If one is virtual, then all are virtual.  */
		  if (TYPE_FN_FIELD_VIRTUAL_P (f, 0))
		    for (j = TYPE_FN_FIELDLIST_LENGTH (basetype, i) - 1; j >= 0; --j)
		      if (TYPE_FN_FIELD_VOFFSET (f, j) == fnoffset)
			{
			  value temp = value_ind (arg2);
			  arg1 = value_virtual_fn_field (&temp, f, j, domain_type, 0);
			  arg2 = value_addr (temp);
			  goto got_it;
			}
		}
	      if (i < 0)
		error ("virtual function at index %d not found", fnoffset);
	    }
	  else
	    {
	      VALUE_TYPE (arg1) = lookup_pointer_type (TYPE_TARGET_TYPE (VALUE_TYPE (arg1)));
	    }
	got_it:

	  /* Now, say which argument to start evaluating from */
	  tem = 2;
	}
      else if (op == STRUCTOP_STRUCT || op == STRUCTOP_PTR)
	{
	  /* Hair for method invocations */
	  int tem2;

	  nargs = longest_to_int (exp->elts[pc + 1].longconst) + 1;
	  /* First, evaluate the structure into arg2 */
	  pc2 = (*pos)++;
	  tem2 = strlen (&exp->elts[pc2 + 1].string);
	  *pos += 2 + (tem2 + sizeof (union exp_element)) / sizeof (union exp_element);
	  if (noside == EVAL_SKIP)
	    goto nosideret;

	  if (op == STRUCTOP_STRUCT)
	    {
	      arg2 = evaluate_subexp_for_address (exp, pos, noside);
	    }
	  else