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From: "slyfox at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug middle-end/98753] -Wfree-nonheap-object on unreachable code
 with -O0
Date: Tue, 26 Jan 2021 19:37:53 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D98753

Sergei Trofimovich <slyfox at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |eike@sf-mail.de,
                   |                            |slyfox at gcc dot gnu.org

--- Comment #10 from Sergei Trofimovich <slyfox at gcc dot gnu.org> ---
Smaller example built from a similar code to cmake:

  // gcc-11.0.0 -c bug.c
  // `void free(void*)` called on unallocated object `b`
[-Wfree-nonheap-object]
  #include <stdlib.h>

  int main(void) {
    char b[1234];
    char * p =3D b;
  #if 0 /* enabled in debug only */
    p =3D (char*)malloc(42);
  #endif
    if (p !=3D b)
        free (p);
  }

$ LANG=3DC gcc-11.0.0 -c bug.c
bug.c: In function 'main':
bug.c:12:9: warning: 'free' called on unallocated object 'b'
[-Wfree-nonheap-object]
   12 |         free (p);
      |         ^~~~~~~~
bug.c:6:10: note: declared here
    6 |     char b[1234];
      |          ^

gcc version 11.0.0 20210112 (experimental) (commit
cfaaa6a1ca744c1a93fa08a3e7ab2a821383cac1)=