[Bug libc/29033] New: Calling 'error' on ppc64le can lead to spurious compiler error with -Wnull-dereference -Werror

[Bug libc/29033] New: Calling 'error' on ppc64le can lead to spurious compiler error with -Wnull-dereference -Werror

[arjun.is at lostca dot se]

https://sourceware.org/bugzilla/show_bug.cgi?id=29033

            Bug ID: 29033
           Summary: Calling 'error' on ppc64le can lead to spurious
                    compiler error with -Wnull-dereference -Werror
           Product: glibc
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: libc
          Assignee: unassigned at sourceware dot org
          Reporter: arjun.is at lostca dot se
                CC: drepper.fsp at gmail dot com
  Target Milestone: ---

misc/bits/error.h has:

/* If we know the function will never return make sure the compiler
   realizes that, too.  */
__extern_always_inline void
error (int __status, int __errnum, const char *__format, ...)
{ 
  if (__builtin_constant_p (__status) && __status != 0)
    __error_noreturn (__status, __errnum, __format, __va_arg_pack ());
  else
    __error_alias (__status, __errnum, __format, __va_arg_pack ());
}


But misc/bits/error-ldbl.h does not have this kind of handling.

Because of this, the following bit of code:

#include <error.h>
#include <stddef.h>
#include <stdlib.h>

struct S
{
  int i;
};

int
main (int argc, char **argv)
{
  struct S ss;
  struct S *s = argv[argc - 1] == NULL ? &ss : NULL;
  if (s == NULL)
    error (EXIT_FAILURE, 0, "frob");

  if (s->i == 0)
    return 1;

  return 0;
}

... when compiled with -Wnull-dereference leads to a warning/error:

$ gcc -Wnull-dereference -Werror -O2 -g test.c
w.c: In function ‘main’:
w.c:18:8: error: potential null pointer dereference [-Werror=null-dereference]
   18 |   if (s->i == 0)
      |       ~^~~
cc1: all warnings being treated as errors

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[Bug libc/29033] Calling 'error' on ppc64le can lead to spurious compiler error with -Wnull-dereference -Werror

[arjun.is at lostca dot se]

https://sourceware.org/bugzilla/show_bug.cgi?id=29033

--- Comment #1 from Arjun Shankar <arjun.is at lostca dot se> ---
I should have mentioned that this is with GCC 12. I was able to reproduce this
on Fedora 36, e.g.

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[Bug libc/29033] Calling 'error' on ppc64le can lead to spurious compiler error with -Wnull-dereference -Werror

[mark at klomp dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=29033

Mark Wielaard <mark at klomp dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mark at klomp dot org

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[Bug libc/29033] Calling 'error' on ppc64le can lead to spurious compiler error with -Wnull-dereference -Werror

[fweimer at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=29033

Florian Weimer <fweimer at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
              Flags|                            |security-
                 CC|                            |fweimer at redhat dot com

--- Comment #2 from Florian Weimer <fweimer at redhat dot com> ---
It requires ieee128 mode, which Fedora 36 uses by default. It should be
reproducible with other GCC versions/distributions with -mabi=ieeelongdouble.

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[Bug libc/29033] Calling 'error' on ppc64le can lead to spurious compiler error with -Wnull-dereference -Werror

[carlos at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=29033

Carlos O'Donell <carlos at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |carlos at redhat dot com,
                   |                            |tuliom at ascii dot art.br

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[Bug libc/29033] Calling 'error' on ppc64le can lead to spurious compiler error with -Wnull-dereference -Werror

[mmatti at linux dot vnet.ibm.com]

https://sourceware.org/bugzilla/show_bug.cgi?id=29033

Manjunath S Matti <mmatti at linux dot vnet.ibm.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mmatti at linux dot vnet.ibm.com

--- Comment #3 from Manjunath S Matti <mmatti at linux dot vnet.ibm.com> ---
This was fixed by
https://sourceware.org/git/?p=glibc.git;a=patch;h=1a57ab0c923f269d1d7c29dfe4634c0ae66d69ac

Can we closed this bug

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[Bug libc/29033] Calling 'error' on ppc64le can lead to spurious compiler error with -Wnull-dereference -Werror

[fweimer at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=29033

Florian Weimer <fweimer at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |2.38
         Resolution|---                         |FIXED
             Status|NEW                         |RESOLVED

--- Comment #4 from Florian Weimer <fweimer at redhat dot com> ---
Fixed for 2.38 via:

commit 1a57ab0c923f269d1d7c29dfe4634c0ae66d69ac
Author: Sachin Monga <smonga@linux.ibm.com>
Date:   Wed May 10 13:59:21 2023 -0400

    Added Redirects to longdouble error functions [BZ #29033]

    This patch redirects the error functions to the appropriate
    longdouble variants which enables the compiler to optimize
    for the abi ieeelongdouble.

    Signed-off-by: Sachin Monga <smonga@linux.ibm.com>

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