개요

• 솔라나라에 설명된 어플리케이션에 대해 맨 페이지를 찾아 출력한다.
• MAN 페이지에 대한 설명은 윈디하나의 솔라나라: MAN 페이지을 참고하자.
• svcadm(8)을 검색하려면 섹션에서 8 을 선택하고, 맨 페이지 이름에 svcadm을 입력하고 검색을 누른다.

malloc_hook(3)

MALLOC_HOOK(3)             Linux Programmer's Manual            MALLOC_HOOK(3)

NAME
       __malloc_hook,  __malloc_initialize_hook, __memalign_hook, __free_hook,
       __realloc_hook, __after_morecore_hook - malloc debugging variables

SYNOPSIS
       #include <malloc.h>

       void *(*__malloc_hook)(size_t size, const void *caller);

       void *(*__realloc_hook)(void *ptr, size_t size, const void *caller);

       void *(*__memalign_hook)(size_t alignment, size_t size,
                                const void *caller);

       void (*__free_hook)(void *ptr, const void *caller);

       void (*__malloc_initialize_hook)(void);

       void (*__after_morecore_hook)(void);

DESCRIPTION
       The GNU C library lets you modify  the  behavior  of  malloc(3),  real‐
       loc(3),  and free(3) by specifying appropriate hook functions.  You can
       use these hooks to help you debug programs that use dynamic memory  al‐
       location, for example.

       The  variable  __malloc_initialize_hook  points  at  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 defin‐
       ition like the following:

           void (*__malloc_initialize_hook)(void) = my_init_hook;

       Now the function my_init_hook() can do the initialization of all hooks.

       The four functions pointed to by __malloc_hook, __realloc_hook, __mema‐
       lign_hook,  __free_hook  have a prototype like the functions malloc(3),
       realloc(3), memalign(3), free(3), respectively, except that they have a
       final argument caller that gives the address  of  the  caller  of  mal‐
       loc(3), etc.

       The  variable __after_morecore_hook points at a function that is called
       each time after sbrk(2) was asked for more memory.

CONFORMING TO
       These functions are GNU extensions.

NOTES
       The use of these hook functions is not safe in multithreaded  programs,
       and  they  are  now  deprecated.   From  glibc 2.24 onwards, the __mal‐
       loc_initialize_hook variable has been removed from the  API.   Program‐
       mers should instead preempt calls to the relevant functions by defining
       and exporting functions such as "malloc" and "free".

EXAMPLE
       Here is a short example of how to use these variables.

       #include <stdio.h>
       #include <malloc.h>

       /* Prototypes for our hooks.  */
       static void my_init_hook(void);
       static void *my_malloc_hook(size_t, const void *);

       /* Variables to save original hooks. */
       static void *(*old_malloc_hook)(size_t, const 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;
           __malloc_hook = my_malloc_hook;
       }

       static void *
       my_malloc_hook(size_t size, const void *caller)
       {
           void *result;

           /* Restore all old hooks */
           __malloc_hook = old_malloc_hook;

           /* Call recursively */
           result = malloc(size);

           /* Save underlying hooks */
           old_malloc_hook = __malloc_hook;

           /* printf() might call malloc(), so protect it too. */
           printf("malloc(%u) called from %p returns %p\n",
                   (unsigned int) size, caller, result);

           /* Restore our own hooks */
           __malloc_hook = my_malloc_hook;

           return result;
       }

SEE ALSO
       mallinfo(3), malloc(3), mcheck(3), mtrace(3)

COLOPHON
       This  page  is  part of release 5.02 of the Linux man-pages project.  A
       description of the project, information about reporting bugs,  and  the
       latest     version     of     this    page,    can    be    found    at
       https://www.kernel.org/doc/man-pages/.

GNU                               2019-03-06                    MALLOC_HOOK(3)