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(c_expand_return): Refine check for returning pointer to local 

variable to allow subtracting a pointer from it.

From-SVN: r8837
This commit is contained in:
Richard Kenner 1995-01-28 15:14:09 -05:00
parent da6f15cdef
commit abe80e6df5
1 changed files with 42 additions and 17 deletions
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59
gcc/c-typeck.c
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@ -1,5 +1,5 @@
/* Build expressions with type checking for C compiler.
Copyright (C) 1987, 88, 91, 92, 93, 1994 Free Software Foundation, Inc.
Copyright (C) 1987, 88, 91, 92, 93, 94, 1995 Free Software Foundation, Inc.
This file is part of GNU CC.
@ -6348,25 +6348,50 @@ c_expand_return (retval)
/* Strip any conversions, additions, and subtractions, and see if
we are returning the address of a local variable. Warn if so. */
while (TREE_CODE (inner) == NOP_EXPR
|| TREE_CODE (inner) == NON_LVALUE_EXPR
|| TREE_CODE (inner) == CONVERT_EXPR
|| TREE_CODE (inner) == PLUS_EXPR
|| TREE_CODE (inner) == MINUS_EXPR)
inner = TREE_OPERAND (inner, 0);
if (TREE_CODE (inner) == ADDR_EXPR)
while (1)
{
inner = TREE_OPERAND (inner, 0);
switch (TREE_CODE (inner))
{
case NOP_EXPR: case NON_LVALUE_EXPR: case CONVERT_EXPR:
case PLUS_EXPR:
inner = TREE_OPERAND (inner, 0);
continue;
while (TREE_CODE_CLASS (TREE_CODE (inner)) == 'r')
inner = TREE_OPERAND (inner, 0);
case MINUS_EXPR:
/* If the second operand of the MINUS_EXPR has a pointer
type (or is converted from it), this may be valid, so
don't give a warning. */
{
tree op1 = TREE_OPERAND (inner, 1);
if (TREE_CODE (inner) == VAR_DECL
&& ! DECL_EXTERNAL (inner)
&& ! TREE_STATIC (inner)
&& DECL_CONTEXT (inner) == current_function_decl)
warning ("function returns address of local variable");
while (! POINTER_TYPE_P (TREE_TYPE (op1))
&& (TREE_CODE (op1) == NOP_EXPR
|| TREE_CODE (op1) == NON_LVALUE_EXPR
|| TREE_CODE (op1) == CONVERT_EXPR))
op1 = TREE_OPERAND (op1, 0);
if (POINTER_TYPE_P (TREE_TYPE (op1)))
break;
inner = TREE_OPERAND (inner, 0);
continue;
}
case ADDR_EXPR:
inner = TREE_OPERAND (inner, 0);
while (TREE_CODE_CLASS (TREE_CODE (inner)) == 'r')
inner = TREE_OPERAND (inner, 0);
if (TREE_CODE (inner) == VAR_DECL
&& ! DECL_EXTERNAL (inner)
&& ! TREE_STATIC (inner)
&& DECL_CONTEXT (inner) == current_function_decl)
warning ("function returns address of local variable");
break;
}
break;
}
t = build (MODIFY_EXPR, TREE_TYPE (res), res, t);