malloc: Remove __malloc_initialize_hook from the API [BZ #19564]

__malloc_initialize_hook is interposed by application code, so
the usual approach to define a compatibility symbol does not work.
This commit adds a new mechanism based on #pragma GCC poison in
<stdc-predef.h>.

malloc/Makefile

@@ -115,6 +115,20 @@ endif
 
 include ../Rules
 
+# Support references to removed APIs.  We use #pragma GCC poison in
+# <stdc-predef.h> to make it difficult to reference them.  For select
+# source files, we work around this poisoning by defining a macro on
+# the command line (which is processed before <stdc-predef.h> and can
+# therefore use tokens poisoned later).
+poisoned_apis = \
+  __malloc_initialize_hook \
+
+unpoisoned_api_defines := \
+  $(foreach sym,$(poisoned_apis), \
+    $(patsubst %,-Dold%, $(sym))=$(sym))
+CPPFLAGS-malloc.c = $(unpoisoned_api_defines)
+CPPFLAGS-mcheck-init.c = $(unpoisoned_api_defines)
+
 CFLAGS-mcheck-init.c = $(PIC-ccflag)
 CFLAGS-obstack.c = $(uses-callbacks)
 

malloc/arena.c

@@ -340,9 +340,11 @@ ptmalloc_init (void)
       if (check_action != 0)
         __malloc_check_init ();
     }
-  void (*hook) (void) = atomic_forced_read (__malloc_initialize_hook);
+#if HAVE_MALLOC_INIT_HOOK
+  void (*hook) (void) = atomic_forced_read (old__malloc_initialize_hook);
   if (hook != NULL)
     (*hook)();
+#endif
   __malloc_initialized = 1;
 }
 

malloc/malloc-hooks.h

@@ -0,0 +1,27 @@
+/* Internal declarations of malloc hooks no longer in the public API.
+   Copyright (C) 2016 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public License as
+   published by the Free Software Foundation; either version 2.1 of the
+   License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; see the file COPYING.LIB.  If
+   not, see <http://www.gnu.org/licenses/>.  */
+
+#ifndef _MALLOC_HOOKS_H
+#define _MALLOC_HOOKS_H
+
+/* These hooks are no longer part of the public API and are poisoned
+   in <stdc-predef.h>.  Their names here reflect the command-line
+   mapping which is used inside glibc to get past the poisoning.  */
+void (*old__malloc_initialize_hook) (void);
+
+#endif  /* _MALLOC_HOOKS_H */

malloc/malloc.c

@@ -491,6 +491,15 @@ void *(*__morecore)(ptrdiff_t) = __default_morecore;
 #define HAVE_MREMAP 0
 #endif
 
+/* We may need to support __malloc_initialize_hook for backwards
+   compatibility.  */
+
+#if SHLIB_COMPAT (libc, GLIBC_2_0, GLIBC_2_24)
+# define HAVE_MALLOC_INIT_HOOK 1
+#else
+# define HAVE_MALLOC_INIT_HOOK 0
+#endif
+
 
 /*
   This version of malloc supports the standard SVID/XPG mallinfo
@@ -1841,7 +1850,12 @@ static void *realloc_hook_ini (void *ptr, size_t sz,
 static void *memalign_hook_ini (size_t alignment, size_t sz,
                                 const void *caller) __THROW;
 
-void weak_variable (*__malloc_initialize_hook) (void) = NULL;
+#if HAVE_MALLOC_INIT_HOOK
+void weak_variable (*old__malloc_initialize_hook) (void) = NULL;
+compat_symbol (libc, old__malloc_initialize_hook,
+	       old__malloc_initialize_hook, GLIBC_2_0);
+#endif
+
 void weak_variable (*__free_hook) (void *__ptr,
                                    const void *) = NULL;
 void *weak_variable (*__malloc_hook)

malloc/malloc.h

@@ -141,11 +141,6 @@ extern void *malloc_get_state (void) __THROW;
    malloc_get_state(). */
 extern int malloc_set_state (void *__ptr) __THROW;
 
-/* Called once when malloc is initialized; redefining this variable in
-   the application provides the preferred way to set up the hook
-   pointers. */
-extern void (*__MALLOC_HOOK_VOLATILE __malloc_initialize_hook) (void)
-__MALLOC_DEPRECATED;
 /* Hooks for debugging and user-defined versions. */
 extern void (*__MALLOC_HOOK_VOLATILE __free_hook) (void *__ptr,
                                                    const void *)

malloc/mcheck-init.c

@@ -27,4 +27,4 @@ turn_on_mcheck (void)
   mcheck (NULL);
 }
 
-void (*__malloc_initialize_hook) (void) = turn_on_mcheck;
+void (*old__malloc_initialize_hook) (void) = turn_on_mcheck;