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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug c++/105346] -Wno-free-nonheap-object false positive (on
 Bison-generated grammar code)
Date: Tue, 26 Apr 2022 09:40:36 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D105346

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|WAITING                     |NEW
           Keywords|                            |diagnostic

--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Tim Van Holder from comment #4)
> Marking as C++ rather than C; while Bison generates C code, here it gets
> compiled in C++ context (with a namespace wrapped around Bison's symbols).

Thanks, I can confirm the diagnostic with -O0, it goes away when optimizing.

The issue seems to be that yyss (or yymsg) are not assigned to anywhere
in the function and so we essentially have

void foo()
{
  char buf[20];
  char *bufp =3D buf;
  if (bufp !=3D buf)
    free (bufp);
}

which we diagnose.  When optimizing the test is optimized away.=