Given the following testcase:
---------------------------------
unsigned char foo;
void test ()
{
foo &= 65280;
foo &= 65280L;
foo &= 65280U;
foo &= 0xff00;
foo &= 0xff00L;
foo &= 0xff00U;
}
---------------------------------
when compiling (gcc -c test.c) there will be warnings emited at first, second,
fourth and fifth expressions but ont at the third and sixth:
test3.c: In function 'test':
test3.c:5: warning: overflow in implicit constant conversion
test3.c:6: warning: overflow in implicit constant conversion
test3.c:9: warning: overflow in implicit constant conversion
test3.c:10: warning: overflow in implicit constant conversion
In my opinion, it should either warn everywhere (overflow because rvalue has
bits set outside of the range of a 'char'), or emit a different warning with
something aboud rvalue signedness.
Also, if you increment all constants by one (e.g. 65281 and 0xff01) all
warnings will disappear. So the warning emited before is either incorrect and
should be never emited in such cases, or should be emited always, but not just
sometimes.
--
Summary: Inconsistent (incorrect?) "overflow in implicit constant
conversion" warning
Product: gcc
Version: 4.3.3
Status: UNCONFIRMED
Severity: minor
Priority: P3
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: anpaza at mail dot ru
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41138
