GCC 6 -Wnonnull is too aggressive

[Petr Spacek]

Hello,

I'm facing problems with new behavior in GCC 6.

Let's assume we have trivial program like this:

$ cat assert.c
#include <assert.h>
#include <stddef.h>

__attribute__((nonnull))
int f(char *txt)  {
        assert(txt != NULL);

        return 0;
}

int main(int argc, char **argv) {

        return 0;
}


And because upstream is paranoid, it is being compiled with:
$ gcc -Werror -Wall


This code does not compile anymore on Fedora 24:
$ gcc -Werror -Wall assert.c
In file included from assert.c:1:0:
assert.c: In function ‘f’:
assert.c:6:13: error: nonnull argument ‘txt’ compared to NULL [-Werror=nonnull]
  assert(txt != NULL);
             ^

Did anyone met similar problem? What did you do with it?

__attribute__((nonnull)) is tremendously useful for static code analysis and
helped to uncover a lot of (not-yet triggered) issues in the code, so just
removing the attribute would not make me happy.

On the other hand, assert(var != NULL) checks are tremendously useful at
run-time. They detects problems early/near the place when the problem occurred
and makes debugging easier.


gcc -Wno-nonnull -fnodelete-null-pointer-checks
does not sound like the right solution ...


I'm all ears to hear what is the best solution/workaround for this.

-- 
Petr Spacek  @  Red Hat