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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>.
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20
ChangeLog
20
ChangeLog
@ -1,3 +1,23 @@
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2016-06-10 Florian Weimer <fweimer@redhat.com>
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[BZ #19564]
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Remove __malloc_initialize_hook from the API.
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* malloc/malloc.h (__malloc_initialize_hook): Remove.
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* include/stdc-predef.h (__malloc_initialize_hook): Poison with
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#pragma GCC poison.
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* malloc/malloc-hooks.h: New file.
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* malloc/arena.c (ptmalloc_init): Use old__malloc_initialize_hook.
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* malloc/malloc.c (HAVE_MALLOC_INIT_HOOK): New.
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(old__malloc_initialize_hook): Rename from
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__malloc_initialize_hook to evade poisoning. Turn into compat
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symbol.
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* malloc/mcheck-init.c (old__malloc_initialize_hook): Rename from
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__malloc_initialize_hook.
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* malloc/Makefile (poisoned_apis, unpoisoned_api_defines): New.
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(mallo.c, mcheck-init.c): Compile with unpoisoned symbol.
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* manual/memory.texi (Hooks for Malloc): Remove
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__malloc_initialize_hook. Adjust hook example.
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2016-06-09 Joseph Myers <joseph@codesourcery.com>
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[BZ #20235]
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3
NEWS
3
NEWS
@ -33,6 +33,9 @@ Version 2.24
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group: files [SUCCESS=merge] nis
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Implemented by Stephen Gallagher (Red Hat).
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* The deprecated __malloc_initialize_hook variable has been removed from the
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API.
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Security related changes:
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* An unnecessary stack copy in _nss_dns_getnetbyname_r was removed. It
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@ -57,4 +57,11 @@
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/* We do not support C11 <threads.h>. */
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#define __STDC_NO_THREADS__ 1
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/* Remove symbols from the API which can be interposed. */
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#if defined (__GNUC__)
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# if __GNUC__ >= 4
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# pragma GCC poison __malloc_initialize_hook
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# endif /* __GNUC__ >= 4 */
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#endif /* __GNUC__ */
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#endif
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@ -115,6 +115,20 @@ endif
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include ../Rules
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# Support references to removed APIs. We use #pragma GCC poison in
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# <stdc-predef.h> to make it difficult to reference them. For select
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# source files, we work around this poisoning by defining a macro on
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# the command line (which is processed before <stdc-predef.h> and can
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# therefore use tokens poisoned later).
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poisoned_apis = \
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__malloc_initialize_hook \
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unpoisoned_api_defines := \
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$(foreach sym,$(poisoned_apis), \
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$(patsubst %,-Dold%, $(sym))=$(sym))
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CPPFLAGS-malloc.c = $(unpoisoned_api_defines)
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CPPFLAGS-mcheck-init.c = $(unpoisoned_api_defines)
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CFLAGS-mcheck-init.c = $(PIC-ccflag)
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CFLAGS-obstack.c = $(uses-callbacks)
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@ -340,9 +340,11 @@ ptmalloc_init (void)
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if (check_action != 0)
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__malloc_check_init ();
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}
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void (*hook) (void) = atomic_forced_read (__malloc_initialize_hook);
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#if HAVE_MALLOC_INIT_HOOK
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void (*hook) (void) = atomic_forced_read (old__malloc_initialize_hook);
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if (hook != NULL)
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(*hook)();
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#endif
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__malloc_initialized = 1;
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}
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27
malloc/malloc-hooks.h
Normal file
27
malloc/malloc-hooks.h
Normal file
@ -0,0 +1,27 @@
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/* Internal declarations of malloc hooks no longer in the public API.
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Copyright (C) 2016 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public License as
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published by the Free Software Foundation; either version 2.1 of the
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License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; see the file COPYING.LIB. If
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not, see <http://www.gnu.org/licenses/>. */
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#ifndef _MALLOC_HOOKS_H
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#define _MALLOC_HOOKS_H
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/* These hooks are no longer part of the public API and are poisoned
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in <stdc-predef.h>. Their names here reflect the command-line
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mapping which is used inside glibc to get past the poisoning. */
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void (*old__malloc_initialize_hook) (void);
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#endif /* _MALLOC_HOOKS_H */
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@ -491,6 +491,15 @@ void *(*__morecore)(ptrdiff_t) = __default_morecore;
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#define HAVE_MREMAP 0
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#endif
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/* We may need to support __malloc_initialize_hook for backwards
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compatibility. */
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#if SHLIB_COMPAT (libc, GLIBC_2_0, GLIBC_2_24)
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# define HAVE_MALLOC_INIT_HOOK 1
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#else
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# define HAVE_MALLOC_INIT_HOOK 0
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#endif
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/*
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This version of malloc supports the standard SVID/XPG mallinfo
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@ -1841,7 +1850,12 @@ static void *realloc_hook_ini (void *ptr, size_t sz,
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static void *memalign_hook_ini (size_t alignment, size_t sz,
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const void *caller) __THROW;
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void weak_variable (*__malloc_initialize_hook) (void) = NULL;
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#if HAVE_MALLOC_INIT_HOOK
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void weak_variable (*old__malloc_initialize_hook) (void) = NULL;
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compat_symbol (libc, old__malloc_initialize_hook,
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old__malloc_initialize_hook, GLIBC_2_0);
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#endif
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void weak_variable (*__free_hook) (void *__ptr,
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const void *) = NULL;
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void *weak_variable (*__malloc_hook)
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@ -141,11 +141,6 @@ extern void *malloc_get_state (void) __THROW;
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malloc_get_state(). */
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extern int malloc_set_state (void *__ptr) __THROW;
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/* Called once when malloc is initialized; redefining this variable in
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the application provides the preferred way to set up the hook
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pointers. */
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extern void (*__MALLOC_HOOK_VOLATILE __malloc_initialize_hook) (void)
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__MALLOC_DEPRECATED;
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/* Hooks for debugging and user-defined versions. */
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extern void (*__MALLOC_HOOK_VOLATILE __free_hook) (void *__ptr,
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const void *)
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@ -27,4 +27,4 @@ turn_on_mcheck (void)
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mcheck (NULL);
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}
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void (*__malloc_initialize_hook) (void) = turn_on_mcheck;
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void (*old__malloc_initialize_hook) (void) = turn_on_mcheck;
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@ -1370,19 +1370,6 @@ should make sure to restore all the hooks to their previous value. When
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coming back from the recursive call, all the hooks should be resaved
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since a hook might modify itself.
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@comment malloc.h
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@comment GNU
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@defvar __malloc_initialize_hook
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The value of this variable is a pointer to a function that is called
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once when the malloc implementation is initialized. This is a weak
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variable, so it can be overridden in the application with a definition
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like the following:
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@smallexample
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void (*@var{__malloc_initialize_hook}) (void) = my_init_hook;
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@end smallexample
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@end defvar
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An issue to look out for is the time at which the malloc hook functions
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can be safely installed. If the hook functions call the malloc-related
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functions recursively, it is necessary that malloc has already properly
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@ -1393,11 +1380,6 @@ are assigned to @emph{before} the very first @code{malloc} call has
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completed, because otherwise a chunk obtained from the ordinary,
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un-hooked malloc may later be handed to @code{__free_hook}, for example.
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In both cases, the problem can be solved by setting up the hooks from
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within a user-defined function pointed to by
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@code{__malloc_initialize_hook}---then the hooks will be set up safely
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at the right time.
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Here is an example showing how to use @code{__malloc_hook} and
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@code{__free_hook} properly. It installs a function that prints out
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information every time @code{malloc} or @code{free} is called. We just
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@ -1413,11 +1395,8 @@ static void my_init_hook (void);
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static void *my_malloc_hook (size_t, const void *);
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static void my_free_hook (void*, const void *);
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/* Override initializing hook from the C library. */
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void (*__malloc_initialize_hook) (void) = my_init_hook;
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static void
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my_init_hook (void)
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my_init (void)
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@{
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old_malloc_hook = __malloc_hook;
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old_free_hook = __free_hook;
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@ -1465,6 +1444,7 @@ my_free_hook (void *ptr, const void *caller)
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main ()
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@{
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my_init ();
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@dots{}
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@}
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@end smallexample
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