[Bug c/92668] New: -Wtautological-compare warns for macros that expand to the same symbol
msebor at gcc dot gnu.org
gcc-bugzilla@gcc.gnu.org
Mon Nov 25 22:25:00 GMT 2019
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92668
Bug ID: 92668
Summary: -Wtautological-compare warns for macros that expand to
the same symbol
Product: gcc
Version: 10.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: msebor at gcc dot gnu.org
Target Milestone: ---
Unlike the C++ front-end and unlike Clang, the C front-end issues
-Wtautological-compare for comparisons involving distinct macros that expand to
the same symbol. GCC should be consistent with itself, and what Clang does
seems reasonable, so probably also with it.
$ cat t.c && gcc -S -Wall -Wextra -Wtautological-compare t.c
int a;
#define X a
#define Y a
int f (void)
{
if (X == Y) return 1;
return 0;
}
t.c: In function ‘f’:
t.c:8:9: warning: self-comparison always evaluates to true
[-Wtautological-compare]
8 | if (X == Y) return 1;
| ^~
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