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1999-11-01  Wolfram Gloger  <wg@malloc.de>

	* malloc/malloc.h: Describe __malloc_initialize_hook.
	* manual/memory.texi: Document __malloc_initialize_hook.

	* sysdeps/unix/sysv/linux/setrlimit.c: Correctly use rlimits.
This commit is contained in:
Ulrich Drepper 1999-11-12 17:15:18 +00:00
parent e78c8e4c26
commit b2f46c3c0e
3 changed files with 52 additions and 8 deletions
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7
ChangeLog
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@ -1,6 +1,11 @@
1999-11-01 Wolfram Gloger <wg@malloc.de>
* malloc/malloc.h: Describe __malloc_initialize_hook.
* manual/memory.texi: Document __malloc_initialize_hook.
1999-11-11 Ulrich Drepper <drepper@cygnus.com>
* sysdeps/unix/sysv/linux/setrlimit.c: COrrectly use rlimits.
* sysdeps/unix/sysv/linux/setrlimit.c: Correctly use rlimits.
1999-11-09 Andreas Jaeger <aj@suse.de>

5
malloc/malloc.h
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@ -206,8 +206,11 @@ extern __malloc_ptr_t malloc_get_state __MALLOC_P ((void));
extern int malloc_set_state __MALLOC_P ((__malloc_ptr_t __ptr));
#if defined __GLIBC__ || defined MALLOC_HOOKS
/* Hooks for debugging versions. */
/* 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_initialize_hook) __MALLOC_PMT ((void));
/* Hooks for debugging and user-defined versions. */
extern void (*__free_hook) __MALLOC_PMT ((__malloc_ptr_t __ptr,
__const __malloc_ptr_t));
extern __malloc_ptr_t (*__malloc_hook) __MALLOC_PMT ((size_t __size,

48
manual/memory.texi
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@ -731,6 +731,34 @@ 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.
@comment malloc.h
@comment GNU
@defvar __malloc_initialize_hook
The value of this variable is a pointer to a function that is called
once when the malloc implementation is initialized. This is a weak
variable, so it can be overridden in the application with a definition
like the following:
@smallexample
void (*@var{__malloc_initialize_hook}) (void) = my_init_hook;
@end smallexample
@end defvar
An issue to look out for is the time at which the malloc hook functions
can be safely installed. If the hook functions call the malloc-related
functions recursively, it is necessary that 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 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 malloc may later be handed to @code{__free_hook}, for example.
In both cases, the problem can be solved by setting up the hooks from
within a user-defined function pointed to by
@code{__malloc_initialize_hook}---then the hooks will be set up safely
at the right time.
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
@ -743,8 +771,21 @@ static void *(*old_malloc_hook) (size_t);
static void (*old_free_hook) (void*);
/* Prototypes for our hooks. */
static void *my_init_hook (void);
static void *my_malloc_hook (size_t);
static void my_free_hook(void*);
static void my_free_hook (void*);
/* Override initializing hook from the C library. */
void (*__malloc_initialize_hook) (void) = my_init_hook;
static void
my_init_hook (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)
@ -787,11 +828,6 @@ my_free_hook (void *ptr)
main ()
@{
...
old_malloc_hook = __malloc_hook;
old_free_hook = __free_hook;
__malloc_hook = my_malloc_hook;
__free_hook = my_free_hook;
...
@}
@end smallexample