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GNU C Library master sources branch master updated. glibc-2.26-575-g8e57c94

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- Log -----------------------------------------------------------------;a=commitdiff;h=8e57c9432a2b68c8a1e7f4df28f0e8c7acc04753

commit 8e57c9432a2b68c8a1e7f4df28f0e8c7acc04753
Author: H.J. Lu <>
Date:   Sun Oct 15 08:16:26 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 â??realloc_checkâ??:
    hooks.c:352:14: error: â??magic_pâ?? may be used uninitialized in this function [-Werror=maybe-uninitialized]
         *magic_p ^= 0xFF;
    due to the GCC bug:
    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 with GCC 7.

diff --git a/ChangeLog b/ChangeLog
index eed7450..17fbe55 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2017-10-15  H.J. Lu  <>
+	[BZ #22052]
+	* malloc/hooks.c (realloc_check): Use DIAG_IGNORE_NEEDS_COMMENT
+	to silence -O3 -Wall warning with GCC 7.
 2017-10-14  H.J. Lu  <>
 	* Makeconfig (+link-static-before-libc): Use the first of
diff --git a/malloc/hooks.c b/malloc/hooks.c
index 01be076..17d8907 100644
--- a/malloc/hooks.c
+++ b/malloc/hooks.c
@@ -345,11 +345,18 @@ realloc_check (void *oldmem, size_t bytes, const void *caller)
       newmem = _int_realloc (&main_arena, oldp, oldsize, nb);
+#if __GNUC_PREREQ (7, 0)
+  /* GCC 7 warns about magic_p may be used uninitialized.  But we never
+     reach here if magic_p is uninitialized.  */
+  DIAG_IGNORE_NEEDS_COMMENT (7, "-Wmaybe-uninitialized");
   /* mem2chunk_check changed the magic byte in the old chunk.
      If newmem is NULL, then the old chunk will still be used though,
      so we need to invert that change here.  */
   if (newmem == NULL)
     *magic_p ^= 0xFF;
   __libc_lock_unlock (main_arena.mutex);


Summary of changes:
 ChangeLog      |    6 ++++++
 malloc/hooks.c |    7 +++++++
 2 files changed, 13 insertions(+), 0 deletions(-)

GNU C Library master sources

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