[Bug tree-optimization/84202] missing -Wnonnull on a returns_nonnull function returning null

[msebor at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84202

Martin Sebor  changed:

   What|Removed |Added

   Last reconfirmed|2018-08-05 00:00:00 |2021-4-8

--- Comment #4 from Martin Sebor  ---
No progress in GCC 11.

Clang diagnoses the first test case:

$ cat pr84202.c && clang -S -Wall pr84202.c

void* __attribute__ ((returns_nonnull)) f ()
{
  return 0;   // missing -Wnonnull
}
pr84202.c:4:3: warning: null returned from function that requires a non-null
  return value [-Wnonnull]
  return 0;   // missing -Wnonnull
  ^  ~
1 warning generated.

[Bug tree-optimization/84202] missing -Wnonnull on a returns_nonnull function returning null

[egallager at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84202

--- Comment #3 from Eric Gallager  ---
(In reply to Martin Sebor from comment #0)
> GCC silently accepts definitions of functions such as f() below declared
> with attribute returns_nonnull.  Clang issues -Wnonnull on functions that
> trivially violate that guarantee.
> 
> void* __attribute__ ((returns_nonnull)) f ()
> {
>   return 0;   // missing -Wnonnull
> }
> 
> Diagnosing trivial mistakes like the one above is only of very limited
> usefulness.  GCC can do much better by also diagnosing functions that might
> return null such as the two below.  Clang doesn't diagnose these.

Maybe split it into a separate -Wmaybe-nonnull for the tougher cases. 

> 
> void* __attribute__ ((returns_nonnull)) g (unsigned n)
> {
>   return __builtin_malloc (n);   // missing -Wnonnull
> }
> 
> void* __attribute__ ((returns_nonnull)) h (unsigned n)
> {
>   static char buf[256];
> 
>   return n < sizeof buf ? buf : __builtin_malloc (n);   // missing -Wnonnull
> }

[Bug tree-optimization/84202] missing -Wnonnull on a returns_nonnull function returning null

[egallager at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84202

Eric Gallager  changed:

   What|Removed |Added

 Status|UNCONFIRMED |NEW
   Last reconfirmed||2018-08-05
 CC||egallager at gcc dot gnu.org
 Ever confirmed|0   |1

--- Comment #2 from Eric Gallager  ---
Confirmed.

[Bug tree-optimization/84202] missing -Wnonnull on a returns_nonnull function returning null

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84202

Martin Sebor  changed:

   What|Removed |Added

 Blocks||58689

--- Comment #1 from Martin Sebor  ---
After some searching I came across bug 58689 that suggests the same thing
(among other returns_nonnull enhancements).  I'm not sure it makes more sense
to resolve this bug as a duplicate of it or to treat bug 58689 as a meta-bug
and link this and any other smaller reports/requests having to do with
returns_nonnull to it.


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58689
[Bug 58689] Enhance returns_nonnull