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(build_binary_op): Warn when ~unsigned is compared against unsigned... 

(build_binary_op): Warn when ~unsigned is compared
against unsigned, and type promotions result in an unexpected answer.

From-SVN: r9670
This commit is contained in:
Doug Evans 1995-05-12 23:22:34 +00:00
parent 2a6f449e66
commit 64c01f8071
1 changed files with 59 additions and 0 deletions
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59
gcc/c-typeck.c
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@ -2453,6 +2453,10 @@ build_binary_op (code, orig_op0, orig_op1, convert_p)
int op0_signed = ! TREE_UNSIGNED (TREE_TYPE (orig_op0));
int op1_signed = ! TREE_UNSIGNED (TREE_TYPE (orig_op1));
int unsignedp0, unsignedp1;
tree primop0 = get_narrower (op0, &unsignedp0);
tree primop1 = get_narrower (op1, &unsignedp1);
/* Avoid spurious warnings for comparison with enumerators. */
xop0 = orig_op0;
@ -2492,6 +2496,61 @@ build_binary_op (code, orig_op0, orig_op1, convert_p)
/* OK */;
else
warning ("comparison between signed and unsigned");
/* Warn if two unsigned values are being compared in a size
larger than their original size, and one (and only one) is the
result of a `~' operator. This comparison will always fail.
Also warn if one operand is a constant, and the constant
does not have all bits set that are set in the ~ operand
when it is extended. */
if ((TREE_CODE (primop0) == BIT_NOT_EXPR)
!= (TREE_CODE (primop1) == BIT_NOT_EXPR))
{
if (TREE_CODE (primop0) == BIT_NOT_EXPR)
primop0 = get_narrower (TREE_OPERAND (primop0, 0),
&unsignedp0);
else
primop1 = get_narrower (TREE_OPERAND (primop1, 0),
&unsignedp1);
if (TREE_CODE (primop0) == INTEGER_CST
|| TREE_CODE (primop1) == INTEGER_CST)
{
tree primop;
long constant, mask;
int unsignedp, bits;
if (TREE_CODE (primop0) == INTEGER_CST)
{
primop = primop1;
unsignedp = unsignedp1;
constant = TREE_INT_CST_LOW (primop0);
}
else
{
primop = primop0;
unsignedp = unsignedp0;
constant = TREE_INT_CST_LOW (primop1);
}
bits = TYPE_PRECISION (TREE_TYPE (primop));
if (bits < TYPE_PRECISION (result_type)
&& bits < HOST_BITS_PER_LONG && unsignedp)
{
mask = (~0L) << bits;
if ((mask & constant) != mask)
warning ("comparison of promoted ~unsigned with constant");
}
}
else if (unsignedp0 && unsignedp1
&& (TYPE_PRECISION (TREE_TYPE (primop0))
< TYPE_PRECISION (result_type))
&& (TYPE_PRECISION (TREE_TYPE (primop1))
< TYPE_PRECISION (result_type)))
warning ("comparison of promoted ~unsigned with unsigned");
}
}
}
}