https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90457
Bug ID: 90457
Summary: -Wimplicit-fallthrough seems confused by #ifdef
Product: gcc
Version: 8.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: gcc-bugs at engestrom dot ch
Target Milestone: ---
Consider the following code:
```
int main(int argc, char *argv[])
{
switch (argc)
{
#ifdef HAVE_FOO
case 1:
if (argv[1])
return 1;
/* fallthrough */
#endif
default:
return 0;
}
}
```
```
$ gcc -Wimplicit-fallthrough foo.c -o foo
```
As expected.
```
$ gcc -Wimplicit-fallthrough foo.c -o foo -DHAVE_FOO
foo.c: In function ‘main’:
foo.c:7:10: warning: this statement may fall through [-Wimplicit-fallthrough=]
if (argv[1])
^
foo.c:11:5: note: here
default:
^~~~~~~
```
This warning should have been suppressed by the comment purposefully left
there.
The same code with the `#ifdef` & `#endif` lines removed behaves as expected
(warning without the comment, no warning with the comment).
It looks like GCC is getting confused by the presence of the #ifdef lines.
