With -Waddress (implied by -Wall), I get the following warning when I use the
test a == 0 where a is an array: the address of 'a' will never be NULL. This
behavior is undocumented and inconsistent (see below). Here's a testcase:
int main (void)
{
char a[1], *b;
b = a;
if (a == 0)
return 1;
else if (a == (void *) 0)
return 2;
else if (b == 0)
return 3;
else if (b == (void *) 0)
return 4;
return 0;
}
gcc warns only for a == 0 (and this is OK to use 0 instead of (void *) 0
because it is a valid form for a null pointer constant).
Moreover this is very similar to code like
if (1) ...
or code given in bug 12963, for which gcc no longer emits warnings: indeed such
kind of correct and useful code is typically used in macros.
--
Summary: spurious and undocumented warning with -Waddress for a
== 0 when a is an array
Product: gcc
Version: 4.3.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: vincent at vinc17 dot org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36299
