https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102558
Bug ID: 102558
Summary: missing warning comparing T[static N] to null
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: msebor at gcc dot gnu.org
Target Milestone: ---
This is the diagnostic part of pr102556:
The C99 [static N] array notation in a function parameter indicates that the
caller must provide as an argument an array with at least N element.
Therefore, in the body of the function, the parameter may be assumed to be
nonnull, the same way as if it had been declared with attribute nonnull.
The test case below shows that GCC fails to issue a warning for the pointless
equality expression in g(), equivalent to the one in f() (although -Waddress
might be more suitable than than -Wnonnull-compare).
$ cat z.c && gcc -O2 -S -Wall z.c
__attribute__ ((nonnull)) int f (int *a)
{
return a == 0; // warning (good, folded to false)
}
int g (int a[static 1])
{
return a == 0; // missing warning (not folded)
}
z.c: In function ‘f’:
z.c:3:12: warning: ‘nonnull’ argument ‘a’ compared to NULL [-Wnonnull-compare]
3 | return a == 0; // warning (good, folded to false)
| ~~^~~~
