linux-kernel - linux-next 20220125 - build failure in objtool with gcc 12

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Message-ID: <20494.1643237814@turing-police>
Date:   Wed, 26 Jan 2022 17:56:54 -0500
From:   "Valdis Klētnieks" <valdis.kletnieks@...edu>
To:     linux-kernel@...r.kernel.org
Subject: linux-next 20220125 - build failure in objtool with gcc 12

Fedora Rawhide shipped gcc12, which apparently includes a new warning that
causes a build failure.  Apparently, it's unable to figure out that 'ptr' remains
valid on failed realloc(), and we only call realloc() again on failures...

  CC      /usr/src/linux-next/tools/objtool/exec-cmd.o
  CC      /usr/src/linux-next/tools/objtool/help.o
In file included from help.c:12:
In function 'xrealloc',
    inlined from 'add_cmdname' at help.c:24:2:
subcmd-util.h:56:23: error: pointer may be used after 'realloc' [-Werror=use-after-free]
   56 |                 ret = realloc(ptr, size);
      |                       ^~~~~~~~~~~~~~~~~~
subcmd-util.h:52:21: note: call to 'realloc' here
   52 |         void *ret = realloc(ptr, size);
      |                     ^~~~~~~~~~~~~~~~~~
subcmd-util.h:58:31: error: pointer may be used after 'realloc' [-Werror=use-after-free]
   58 |                         ret = realloc(ptr, 1);
      |                               ^~~~~~~~~~~~~~~
subcmd-util.h:52:21: note: call to 'realloc' here
   52 |         void *ret = realloc(ptr, size);
      |                     ^~~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors
make[4]: *** [/usr/src/linux-next/tools/build/Makefile.build:97: /usr/src/linux-next/tools/objtool/help.o] Error 1
make[3]: *** [Makefile:59: /usr/src/linux-next/tools/objtool/libsubcmd-in.o] Error 2
make[2]: *** [Makefile:63: /usr/src/linux-next/tools/objtool/libsubcmd.a] Error 2
make[1]: *** [Makefile:69: objtool] Error 2
make: *** [Makefile:1405: tools/objtool] Error 2


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