@@ -103,6 +103,16 @@ Deprecated and removed features, and other changes affecting compatibility:
features now need to preload a new debugging DSO libc_malloc_debug.so to get
this functionality back.
+* The deprecated memory allocation hooks __malloc_hook, __realloc_hook,
+ __memalign_hook and __free_hook are now removed from the API. Compatibility
+ symbols are present to support legacy programs but new applications can no
+ longer link to these symbols. These hooks no longer have any effect on glibc
+ functionality. The malloc debugging DSO libc_malloc_debug.so currently
+ supports hooks and can be preloaded to get this functionality back for older
+ programs. However this is a transitional measure and may be removed in a
+ future release of the GNU C Library. Users may port away from these hooks by
+ writing and preloading their own malloc interposition library.
+
Changes to build and runtime requirements:
* On Linux, the shm_open, sem_open, and related functions now expect the
@@ -23,17 +23,22 @@ compat_symbol (libc, __malloc_initialize_hook,
__malloc_initialize_hook, GLIBC_2_0);
#endif
+#if SHLIB_COMPAT (libc, GLIBC_2_0, GLIBC_2_34)
static void *malloc_hook_ini (size_t, const void *) __THROW;
static void *realloc_hook_ini (void *, size_t, const void *) __THROW;
static void *memalign_hook_ini (size_t, size_t, const void *) __THROW;
void weak_variable (*__free_hook) (void *, const void *) = NULL;
+compat_symbol (libc, __free_hook, __free_hook, GLIBC_2_0);
void *weak_variable (*__malloc_hook)
(size_t, const void *) = malloc_hook_ini;
+compat_symbol (libc, __malloc_hook, __malloc_hook, GLIBC_2_0);
void *weak_variable (*__realloc_hook)
(void *, size_t, const void *) = realloc_hook_ini;
+compat_symbol (libc, __realloc_hook, __realloc_hook, GLIBC_2_0);
void *weak_variable (*__memalign_hook)
(size_t, size_t, const void *) = memalign_hook_ini;
+compat_symbol (libc, __memalign_hook, __memalign_hook, GLIBC_2_0);
/* This is interposed by libc_malloc_debug.so to match with a compatible libc.
We don't use dlsym or equivalent because the dlsym symbol version got bumped
@@ -87,6 +92,7 @@ memalign_hook_ini (size_t alignment, size_t sz, const void *caller)
generic_hook_ini ();
return memalign (alignment, sz);
}
+#endif
static bool force_malloc_check_off = false;
deleted file mode 100644
@@ -1,24 +0,0 @@
-/* Internal declarations of malloc hooks no longer in the public API.
- Copyright (C) 2016-2021 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 <https://www.gnu.org/licenses/>. */
-
-#ifndef _MALLOC_HOOKS_H
-#define _MALLOC_HOOKS_H
-
-void (*__malloc_initialize_hook) (void);
-
-#endif /* _MALLOC_HOOKS_H */
@@ -165,20 +165,6 @@ extern void malloc_stats (void) __THROW;
extern int malloc_info (int __options, FILE *__fp) __THROW;
/* Hooks for debugging and user-defined versions. */
-extern void (*__MALLOC_HOOK_VOLATILE __free_hook) (void *__ptr,
- const void *)
-__MALLOC_DEPRECATED;
-extern void *(*__MALLOC_HOOK_VOLATILE __malloc_hook)(size_t __size,
- const void *)
-__MALLOC_DEPRECATED;
-extern void *(*__MALLOC_HOOK_VOLATILE __realloc_hook)(void *__ptr,
- size_t __size,
- const void *)
-__MALLOC_DEPRECATED;
-extern void *(*__MALLOC_HOOK_VOLATILE __memalign_hook)(size_t __alignment,
- size_t __size,
- const void *)
-__MALLOC_DEPRECATED;
extern void (*__MALLOC_HOOK_VOLATILE __after_morecore_hook) (void)
__MALLOC_DEPRECATED;
@@ -328,8 +328,6 @@ any time (or never).
* Malloc Tunable Parameters:: Use @code{mallopt} to adjust allocation
parameters.
* Heap Consistency Checking:: Automatic checking for errors.
-* Hooks for Malloc:: You can use these hooks for debugging
- programs that use @code{malloc}.
* Statistics of Malloc:: Getting information about how much
memory your program is using.
* Summary of Malloc:: Summary of @code{malloc} and related functions.
@@ -1392,170 +1390,6 @@ compatibility. Both @code{MALLOC_CHECK_} and @samp{-lmcheck} should
uncover the same bugs - but using @code{MALLOC_CHECK_} you don't need to
recompile your application.
-@node Hooks for Malloc
-@subsubsection Memory Allocation Hooks
-@cindex allocation hooks, for @code{malloc}
-
-@Theglibc{} lets you modify the behavior of @code{malloc},
-@code{realloc}, and @code{free} by specifying appropriate hook
-functions. You can use these hooks to help you debug programs that use
-dynamic memory allocation, for example.
-
-The hook variables are declared in @file{malloc.h}.
-@pindex malloc.h
-
-@defvar __malloc_hook
-@standards{GNU, malloc.h}
-The value of this variable is a pointer to the function that
-@code{malloc} uses whenever it is called. You should define this
-function to look like @code{malloc}; that is, like:
-
-@smallexample
-void *@var{function} (size_t @var{size}, const void *@var{caller})
-@end smallexample
-
-The value of @var{caller} is the return address found on the stack when
-the @code{malloc} function was called. This value allows you to trace
-the memory consumption of the program.
-@end defvar
-
-@defvar __realloc_hook
-@standards{GNU, malloc.h}
-The value of this variable is a pointer to function that @code{realloc}
-uses whenever it is called. You should define this function to look
-like @code{realloc}; that is, like:
-
-@smallexample
-void *@var{function} (void *@var{ptr}, size_t @var{size}, const void *@var{caller})
-@end smallexample
-
-The value of @var{caller} is the return address found on the stack when
-the @code{realloc} function was called. This value allows you to trace the
-memory consumption of the program.
-@end defvar
-
-@defvar __free_hook
-@standards{GNU, malloc.h}
-The value of this variable is a pointer to function that @code{free}
-uses whenever it is called. You should define this function to look
-like @code{free}; that is, like:
-
-@smallexample
-void @var{function} (void *@var{ptr}, const void *@var{caller})
-@end smallexample
-
-The value of @var{caller} is the return address found on the stack when
-the @code{free} function was called. This value allows you to trace the
-memory consumption of the program.
-@end defvar
-
-@defvar __memalign_hook
-@standards{GNU, malloc.h}
-The value of this variable is a pointer to function that @code{aligned_alloc},
-@code{memalign}, @code{posix_memalign} and @code{valloc} use whenever they
-are called. You should define this function to look like @code{aligned_alloc};
-that is, like:
-
-@smallexample
-void *@var{function} (size_t @var{alignment}, size_t @var{size}, const void *@var{caller})
-@end smallexample
-
-The value of @var{caller} is the return address found on the stack when
-the @code{aligned_alloc}, @code{memalign}, @code{posix_memalign} or
-@code{valloc} functions are called. This value allows you to trace the
-memory consumption of the program.
-@end defvar
-
-You must make sure that the function you install as a hook for one of
-these functions does not call that function recursively without restoring
-the old value of the hook first! Otherwise, your program will get stuck
-in an infinite recursion. Before calling the function recursively, one
-should make sure to restore all the hooks to their previous value. When
-coming back from the recursive call, all the hooks should be resaved
-since a hook might modify itself.
-
-An issue to look out for is the time at which the hook functions
-can be safely installed. If the hook functions call the @code{malloc}-related
-functions recursively, it is necessary that @code{malloc} has already properly
-initialized itself at the time when @code{__malloc_hook} etc. is
-assigned to. On the other hand, if the hook functions provide a
-complete @code{malloc} implementation of their own, it is vital that the hooks
-are assigned to @emph{before} the very first @code{malloc} call has
-completed, because otherwise a chunk obtained from the ordinary,
-un-hooked @code{malloc} may later be handed to @code{__free_hook}, for example.
-
-Here is an example showing how to use @code{__malloc_hook} and
-@code{__free_hook} properly. It installs a function that prints out
-information every time @code{malloc} or @code{free} is called. We just
-assume here that @code{realloc} and @code{memalign} are not used in our
-program.
-
-@smallexample
-/* Prototypes for __malloc_hook, __free_hook */
-#include <malloc.h>
-
-/* Prototypes for our hooks. */
-static void my_init_hook (void);
-static void *my_malloc_hook (size_t, const void *);
-static void my_free_hook (void*, const void *);
-
-static void
-my_init (void)
-@{
- old_malloc_hook = __malloc_hook;
- old_free_hook = __free_hook;
- __malloc_hook = my_malloc_hook;
- __free_hook = my_free_hook;
-@}
-
-static void *
-my_malloc_hook (size_t size, const void *caller)
-@{
- void *result;
- /* Restore all old hooks */
- __malloc_hook = old_malloc_hook;
- __free_hook = old_free_hook;
- /* Call recursively */
- result = malloc (size);
- /* Save underlying hooks */
- old_malloc_hook = __malloc_hook;
- old_free_hook = __free_hook;
- /* @r{@code{printf} might call @code{malloc}, so protect it too.} */
- printf ("malloc (%u) returns %p\n", (unsigned int) size, result);
- /* Restore our own hooks */
- __malloc_hook = my_malloc_hook;
- __free_hook = my_free_hook;
- return result;
-@}
-
-static void
-my_free_hook (void *ptr, const void *caller)
-@{
- /* Restore all old hooks */
- __malloc_hook = old_malloc_hook;
- __free_hook = old_free_hook;
- /* Call recursively */
- free (ptr);
- /* Save underlying hooks */
- old_malloc_hook = __malloc_hook;
- old_free_hook = __free_hook;
- /* @r{@code{printf} might call @code{free}, so protect it too.} */
- printf ("freed pointer %p\n", ptr);
- /* Restore our own hooks */
- __malloc_hook = my_malloc_hook;
- __free_hook = my_free_hook;
-@}
-
-main ()
-@{
- my_init ();
- @dots{}
-@}
-@end smallexample
-
-The @code{mcheck} function (@pxref{Heap Consistency Checking}) works by
-installing such hooks.
-
@c __morecore, __after_morecore_hook are undocumented
@c It's not clear whether to document them.
@@ -1690,19 +1524,6 @@ Tell @code{malloc} to perform occasional consistency checks on
dynamically allocated memory, and to call @var{abortfn} when an
inconsistency is found. @xref{Heap Consistency Checking}.
-@item void *(*__malloc_hook) (size_t @var{size}, const void *@var{caller})
-A pointer to a function that @code{malloc} uses whenever it is called.
-
-@item void *(*__realloc_hook) (void *@var{ptr}, size_t @var{size}, const void *@var{caller})
-A pointer to a function that @code{realloc} uses whenever it is called.
-
-@item void (*__free_hook) (void *@var{ptr}, const void *@var{caller})
-A pointer to a function that @code{free} uses whenever it is called.
-
-@item void (*__memalign_hook) (size_t @var{size}, size_t @var{alignment}, const void *@var{caller})
-A pointer to a function that @code{aligned_alloc}, @code{memalign},
-@code{posix_memalign} and @code{valloc} use whenever they are called.
-
@item struct mallinfo2 mallinfo2 (void)
Return information about the current dynamic memory usage.
@xref{Statistics of Malloc}.
@@ -1737,7 +1558,7 @@ penalties for the program if the debugging mode is not enabled.
@deftypefun void mtrace (void)
@standards{GNU, mcheck.h}
-@safety{@prelim{}@mtunsafe{@mtsenv{} @mtasurace{:mtrace} @mtasuconst{:malloc_hooks} @mtuinit{}}@asunsafe{@asuinit{} @ascuheap{} @asucorrupt{} @asulock{}}@acunsafe{@acuinit{} @acucorrupt{} @aculock{} @acsfd{} @acsmem{}}}
+@safety{@prelim{}@mtunsafe{@mtsenv{} @mtasurace{:mtrace} @mtuinit{}}@asunsafe{@asuinit{} @ascuheap{} @asucorrupt{} @asulock{}}@acunsafe{@acuinit{} @acucorrupt{} @aculock{} @acsfd{} @acsmem{}}}
@c Like the mcheck hooks, these are not designed with thread safety in
@c mind, because the hook pointers are temporarily modified without
@c regard to other threads, signals or cancellation.
@@ -1768,10 +1589,10 @@ with the SUID or SGID bit set.
If the named file is successfully opened, @code{mtrace} installs special
handlers for the functions @code{malloc}, @code{realloc}, and
-@code{free} (@pxref{Hooks for Malloc}). From then on, all uses of these
-functions are traced and protocolled into the file. There is now of
-course a speed penalty for all calls to the traced functions so tracing
-should not be enabled during normal use.
+@code{free}. From then on, all uses of these functions are traced and
+protocolled into the file. There is now of course a speed penalty for all
+calls to the traced functions so tracing should not be enabled during normal
+use.
This function is a GNU extension and generally not available on other
systems. The prototype can be found in @file{mcheck.h}.
@@ -1779,7 +1600,7 @@ systems. The prototype can be found in @file{mcheck.h}.
@deftypefun void muntrace (void)
@standards{GNU, mcheck.h}
-@safety{@prelim{}@mtunsafe{@mtasurace{:mtrace} @mtasuconst{:malloc_hooks} @mtslocale{}}@asunsafe{@asucorrupt{} @ascuheap{}}@acunsafe{@acucorrupt{} @acsmem{} @aculock{} @acsfd{}}}
+@safety{@prelim{}@mtunsafe{@mtasurace{:mtrace} @mtslocale{}}@asunsafe{@asucorrupt{} @ascuheap{}}@acunsafe{@acucorrupt{} @acsmem{} @aculock{} @acsfd{}}}
@c muntrace @mtasurace:mtrace @mtslocale @asucorrupt @ascuheap @acucorrupt @acsmem @aculock @acsfd
@c fprintf (fputs) dup @mtslocale @asucorrupt @ascuheap @acsmem @aculock @acucorrupt