https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84316
Martin Sebor <msebor at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Keywords| |diagnostic
Summary|-Wnull-dereference doesn't |missing -Wnull-dereference
|work with LTO |on a variable null array
| |reference with LTO
--- Comment #1 from Martin Sebor <msebor at gcc dot gnu.org> ---
With more testing I see that the -Wnull-dereference option actually does work
with LTO, it's just prone to false negatives. Below is a variant of the test
case for -Wnonnull. It triggers -Wnull-dereference for the constant zero index
but it doesn't trigger -Wnonnull.
$ (set -x; cat a.c; cc='gcc -O3 -Wall -Wextra -Wnull-dereference -flto'; $cc -c
a.c && $cc -DMAIN -c -o main.o a.c && $cc a.o main.o)
+ cat a.c
#if MAIN
extern int f (const char*);
int main (void)
{
char *s = 0;
return f (s);
}
#else
static int __attribute__ ((nonnull (1)))
g (const char *s)
{
return __builtin_strlen (s);
}
int f (const char *s)
{
return s[0] ? g (s) : 0; // -Wnull-dereference here (good)
}
#endif
+ cc='gcc -O3 -Wall -Wextra -Wnull-dereference -flto'
+ gcc -O3 -Wall -Wextra -Wnull-dereference -flto -c a.c
+ gcc -O3 -Wall -Wextra -Wnull-dereference -flto -DMAIN -c -o main.o a.c
+ gcc -O3 -Wall -Wextra -Wnull-dereference -flto a.o main.o
a.c: In function ‘main’:
a.c:21:11: warning: null pointer dereference [-Wnull-dereference]
return s[0] ? g (s) : 0;
^
