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[Bug malloc/22052] malloc failed to compile with GCC 7 and -O3

--- Comment #1 from cvs-commit at gcc dot <cvs-commit at gcc dot> ---
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The branch, hjl/pr22298/master has been created
        at  16be5568a0c24b9bd1ade7fa937c94b5d53b6ab1 (commit)

- Log -----------------------------------------------------------------;h=16be5568a0c24b9bd1ade7fa937c94b5d53b6ab1

commit 16be5568a0c24b9bd1ade7fa937c94b5d53b6ab1
Author: H.J. Lu <>
Date:   Sun Oct 15 07:48:58 2017 -0700

    Define __PTHREAD_MUTEX_HAVE_PREV only if undefined [BZ #22298]

    It is incorrect to define __PTHREAD_MUTEX_HAVE_PREV to 1 only when
    __WORDSIZE == 64.  For x32, __PTHREAD_MUTEX_HAVE_PREV should be 1, but
    it has __WORDSIZE == 32.  This patch defines __PTHREAD_MUTEX_HAVE_PREV
    based on __WORDSIZE only if it is undefined.  __PTHREAD_MUTEX_HAVE_PREV
    check is changed from "#ifdef" to "#if" to support values of 0 or 1.

        [BZ #22298]
        * nptl/allocatestack.c (allocate_stack): Check if
        __PTHREAD_MUTEX_HAVE_PREV is non-zero, instead if
        __PTHREAD_MUTEX_HAVE_PREV is defined.
        * nptl/descr.h (pthread): Likewise.
        * nptl/nptl-init.c (__pthread_initialize_minimal_internal):
        * nptl/pthread_create.c (START_THREAD_DEFN): Likewise.
        * sysdeps/nptl/fork.c (__libc_fork): Likewise.
        * sysdeps/nptl/pthread.h (PTHREAD_MUTEX_INITIALIZER): Likewise.
        * sysdeps/nptl/bits/thread-shared-types.h
        (__PTHREAD_MUTEX_HAVE_PREV): Define only if it is undefined.
        (__pthread_internal_list): Check __pthread_internal_list instead
        of __WORDSIZE.
        (__PTHREAD_SPINS_DATA): Likewise.
        (__PTHREAD_SPINS): Likewise.
        (__pthread_mutex_s): Likewise.
        * sysdeps/x86/nptl/bits/pthreadtypes-arch.h
        (__PTHREAD_MUTEX_HAVE_PREV): Defined.;h=df44f9d02b68de45ba8c3984f47ecf1a523306ec

commit df44f9d02b68de45ba8c3984f47ecf1a523306ec
Author: H.J. Lu <>
Date:   Sun Oct 15 07:23:41 2017 -0700

    x32: Verify that NPTL structures are correct [BZ #22298]

    Add a build-time check to verify that NPTL structures are correct.

        * sysdeps/x86_64/x32/nptl/Makefile: New file.
        * sysdeps/x86_64/x32/nptl/nptl-check.sym: Likewise.;h=aca3e9b42f9c172af368f2fc54d2c7299b231cc0

commit aca3e9b42f9c172af368f2fc54d2c7299b231cc0
Author: H.J. Lu <>
Date:   Sun Sep 3 08:39:55 2017 -0700

    Silence -O3 -Wall warning in malloc/hooks.c with GCC 7 [BZ #22052]

    realloc_check has

      unsigned char *magic_p;
      __libc_lock_lock (main_arena.mutex);
      const mchunkptr oldp = mem2chunk_check (oldmem, &magic_p);
      __libc_lock_unlock (main_arena.mutex);
      if (!oldp)
        malloc_printerr ("realloc(): invalid pointer");
      if (newmem == NULL)
        *magic_p ^= 0xFF;


    static void malloc_printerr(const char *str) __attribute__ ((noreturn));

    GCC 7 -O3 warns

    hooks.c: In function ‘realloc_check’:
    hooks.c:352:14: error: ‘magic_p’ may be used uninitialized in this function
         *magic_p ^= 0xFF;

    This patch silences GCC 7 by using DIAG_IGNORE_NEEDS_COMMENT.

        [BZ #22052]
        * malloc/hooks.c (realloc_check): Use DIAG_IGNORE_NEEDS_COMMENT
        to silence -O3 -Wall warning GCC 7.


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