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c-family: One more 40752 tweak for unsigned char.

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My last patch didn't fix all the failures on unsignd char targets.  We were
missing one warning because by suppressing -Wsign-conversion for the second
operand of + we missed an overflow that we want to warn about, and we
properly don't warn about unsigned / or %.

	PR testsuite/93391 - PR 40752 test fails with unsigned plain char.
	* c-warn.c (conversion_warning): Change -Wsign-conversion handling.
	* lib/target-supports.exp (check_effective_target_unsigned_char):
	New.
This commit is contained in:
Jason Merrill 2020-01-23 10:37:18 -05:00
parent 54b3d52c3c
commit 6d00f052ef
5 changed files with 27 additions and 5 deletions

4
gcc/c-family/ChangeLog

@ -1,3 +1,7 @@
2020-01-23 Jason Merrill <jason@redhat.com>
* c-warn.c (conversion_warning): Change -Wsign-conversion handling.
2020-01-23 Martin Sebor <msebor@redhat.com>
PR c/84919

10
gcc/c-family/c-warn.c

@ -1315,10 +1315,14 @@ conversion_warning (location_t loc, tree type, tree expr, tree result)
for (int i = 0; i < arith_ops; ++i)
{
tree op = TREE_OPERAND (expr, i);
tree opr = convert (type, op);
/* Avoid -Wsign-conversion for (unsigned)(x + (-1)). */
bool minus = TREE_CODE (expr) == PLUS_EXPR && i == 1;
if (unsafe_conversion_p (type, op, opr, !minus))
if (TREE_CODE (expr) == PLUS_EXPR && i == 1
&& INTEGRAL_TYPE_P (type) && TYPE_UNSIGNED (type)
&& TREE_CODE (op) == INTEGER_CST
&& tree_int_cst_sgn (op) < 0)
op = fold_build1 (NEGATE_EXPR, TREE_TYPE (op), op);
tree opr = convert (type, op);
if (unsafe_conversion_p (type, op, opr, true))
goto op_unsafe;
}
/* The operands seem safe, we might still want to warn if

5
gcc/testsuite/ChangeLog

@ -1,3 +1,8 @@
2020-01-23 Jason Merrill <jason@redhat.com>
* lib/target-supports.exp (check_effective_target_unsigned_char):
New.
2020-01-23 Jakub Jelinek <jakub@redhat.com>
PR target/93376

5
gcc/testsuite/c-c++-common/Wconversion-pr40752a.c

@ -14,9 +14,10 @@ void foo(char c, char c2)
c *= 2; /* { dg-warning "conversion" } */
c *= c2; /* { dg-warning "conversion" } */
c /= 2;
c /= c2; /* { dg-warning "conversion" } */
/* If char is unsigned we avoid promoting to int. */
c /= c2; /* { dg-warning "conversion" "" { target { ! unsigned_char } } } */
c %= 2;
c %= c2; /* { dg-warning "conversion" } */
c %= c2; /* { dg-warning "conversion" "" { target { ! unsigned_char } } } */
c = -c2; /* { dg-warning "conversion" } */
c = ~c2; /* { dg-warning "conversion" } */
c = c2++;

8
gcc/testsuite/lib/target-supports.exp

@ -3115,6 +3115,14 @@ proc check_effective_target_dfprt { } {
}]
}
# Return 1 iff target has unsigned plain 'char' by default.
proc check_effective_target_unsigned_char {} {
return [check_no_compiler_messages unsigned_char assembly {
char ar[(char)-1];
}]
}
proc check_effective_target_powerpc_popcntb_ok { } {
return [check_cached_effective_target powerpc_popcntb_ok {