https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100605
Bug ID: 100605
Summary: -Wimplicit-fallthrough=5 still recognizes comments
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: tuliom at ascii dot art.br
Target Milestone: ---
According to the GCC manual:
"-Wimplicit-fallthrough=5 doesn’t recognize any comments as fallthrough
comments, only attributes disable the warning."
However, comments are still being recognized and are disabling the warning.
In the following example, there are 3 fall-throughs:
$ cat t.c
#include <stddef.h>
#include <inttypes.h>
uint32_t foo(size_t in)
{
uint32_t out = 0;
uint32_t k = 0;
switch (in & 3)
{
case 3:
k = 3;
// FALLTHROUGH
case 2:
k = 8;
case 1:
k = 16;
case 0:
default:
out = k;
break;
}
return out;
}
However, GCC 11 reports only 2 when using -Wimplicit-fallthrough=5:
$ gcc-11 -c -Wimplicit-fallthrough=5 -Werror=implicit-fallthrough t.c
t.c: In function ‘foo’:
t.c:15:9: error: this statement may fall through
[-Werror=implicit-fallthrough=]
15 | k = 8;
| ~~^~~
t.c:16:5: note: here
16 | case 1:
| ^~~~
t.c:17:9: error: this statement may fall through
[-Werror=implicit-fallthrough=]
17 | k = 16;
| ~~^~~~
t.c:18:5: note: here
18 | case 0:
| ^~~~
cc1: some warnings being treated as errors
