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re PR c/51712 (-Wtype-limits should not trigger for types of implementation-defined signedness)

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2012-05-04  Manuel López-Ibáñez  <manu@gcc.gnu.org>

	PR c/51712
c-family/
	* c-common.c (expr_original_type): New.
	(shorten_compare): Do not warn for enumeration types.
testsuite/
	* c-c++-common/pr51712.c: New.

From-SVN: r187125
This commit is contained in:
Manuel López-Ibáñez 2012-05-03 22:37:01 +00:00
parent 0c3641b0ea
commit 50f305cacf
4 changed files with 61 additions and 18 deletions
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6
gcc/c-family/ChangeLog
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@ -1,3 +1,9 @@
2012-05-04 Manuel López-Ibáñez <manu@gcc.gnu.org>
PR c/51712
* c-common.c (expr_original_type): New.
(shorten_compare): Do not warn for enumeration types.
2012-05-03 Manuel López-Ibáñez <manu@gcc.gnu.org>
* c.opt (fpermissive): Add Var(flag_permissive).

50
gcc/c-family/c-common.c
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@ -3481,6 +3481,15 @@ binary_op_error (location_t location, enum tree_code code,
type0, type1);
}
/* Given an expression as a tree, return its original type. Do this
by stripping any conversion that preserves the sign and precision. */
static tree
expr_original_type (tree expr)
{
STRIP_SIGN_NOPS (expr);
return TREE_TYPE (expr);
}
/* Subroutine of build_binary_op, used for comparison operations.
See if the operands have both been converted from subword integer types
and, if so, perhaps change them both back to their original type.
@ -3506,6 +3515,7 @@ shorten_compare (tree *op0_ptr, tree *op1_ptr, tree *restype_ptr,
int real1, real2;
tree primop0, primop1;
enum tree_code code = *rescode_ptr;
location_t loc = EXPR_LOC_OR_HERE (op0);
/* Throw away any conversions to wider types
already present in the operands. */
@ -3726,9 +3736,11 @@ shorten_compare (tree *op0_ptr, tree *op1_ptr, tree *restype_ptr,
if (TREE_CODE (primop0) != INTEGER_CST)
{
if (val == truthvalue_false_node)
warning (OPT_Wtype_limits, "comparison is always false due to limited range of data type");
warning_at (loc, OPT_Wtype_limits,
"comparison is always false due to limited range of data type");
if (val == truthvalue_true_node)
warning (OPT_Wtype_limits, "comparison is always true due to limited range of data type");
warning_at (loc, OPT_Wtype_limits,
"comparison is always true due to limited range of data type");
}
if (val != 0)
@ -3795,29 +3807,31 @@ shorten_compare (tree *op0_ptr, tree *op1_ptr, tree *restype_ptr,
&& TYPE_UNSIGNED (*restype_ptr))
{
tree value = 0;
/* All unsigned values are >= 0, so we warn. However,
if OP0 is a constant that is >= 0, the signedness of
the comparison isn't an issue, so suppress the
warning. */
bool warn =
warn_type_limits && !in_system_header
&& !(TREE_CODE (primop0) == INTEGER_CST
&& !TREE_OVERFLOW (convert (c_common_signed_type (type),
primop0)))
/* Do not warn for enumeration types. */
&& (TREE_CODE (expr_original_type (primop0)) != ENUMERAL_TYPE);
switch (code)
{
case GE_EXPR:
/* All unsigned values are >= 0, so we warn. However,
if OP0 is a constant that is >= 0, the signedness of
the comparison isn't an issue, so suppress the
warning. */
if (warn_type_limits && !in_system_header
&& !(TREE_CODE (primop0) == INTEGER_CST
&& !TREE_OVERFLOW (convert (c_common_signed_type (type),
primop0))))
warning (OPT_Wtype_limits,
"comparison of unsigned expression >= 0 is always true");
if (warn)
warning_at (loc, OPT_Wtype_limits,
"comparison of unsigned expression >= 0 is always true");
value = truthvalue_true_node;
break;
case LT_EXPR:
if (warn_type_limits && !in_system_header
&& !(TREE_CODE (primop0) == INTEGER_CST
&& !TREE_OVERFLOW (convert (c_common_signed_type (type),
primop0))))
warning (OPT_Wtype_limits,
"comparison of unsigned expression < 0 is always false");
if (warn)
warning_at (loc, OPT_Wtype_limits,
"comparison of unsigned expression < 0 is always false");
value = truthvalue_false_node;
break;

5
gcc/testsuite/ChangeLog
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@ -1,3 +1,8 @@
2012-05-04 Manuel López-Ibáñez <manu@gcc.gnu.org>
PR c/51712
* c-c++-common/pr51712.c: New.
2012-05-03 Michael Meissner <meissner@linux.vnet.ibm.com>
PR target/53199

18
gcc/testsuite/c-c++-common/pr51712.c Normal file
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@ -0,0 +1,18 @@
/* PR c/51712 */
/* { dg-do compile } */
/* { dg-options "-Wtype-limits" } */
enum test_enum {
FOO,
BAR
};
int valid(enum test_enum arg)
{
return arg >= 0 && arg <= BAR;
}
int valid2(unsigned int arg2)
{
return arg2 >= FOO && arg2 <= BAR; /* { dg-bogus "comparison of unsigned expression" "" { xfail *-*-* } } */
}