[Bug c/25509] can't disable __attribute__((warn_unused_result))

[ppluzhnikov at google dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=25509

Paul Pluzhnikov <ppluzhnikov at google dot com> changed:

           What    |Removed                     |Added
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                 CC|                            |ppluzhnikov at google dot com

--- Comment #28 from Paul Pluzhnikov <ppluzhnikov at google dot com> ---
Google ref: b/16983603.

I wouldn't call this bug fixed.

I have just found ~30 bugs in our code, where someone wrote:

  vector<int> v;
  ...
  v.empty();   // v.clear() was intended!

No problem, I'll just add warn_unused_result to vector::empty(), right?

Well, that did expose the 30 bugs above, but unfortunately I can't do that
permanently, because it also exposed this false positive:

   assert(v.empty());

where assert in NDEBUG mode expanded into

  static_cast<void>(v.empty());

and triggered the warning :-(

P.S. Some of the bugs I found were in parts of the code imported from
open-source projects, so it's not a problem that is specific to just Google. If
the assert problem could be addressed, adding warn_unused_result to trunk
libstdc++ would benefit everyone.