[PATCH v4 10/10] Remove __morecore and __default_morecore

[Carlos O'Donell]

On 7/2/21 7:38 AM, Siddhesh Poyarekar wrote:
> Make the __morecore and __default_morecore symbols compat-only and
> remove their declarations from the API.

LGTM.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>
 
> Reviewed-by: DJ Delorie <dj@redhat.com>
> ---
>  NEWS                     |  5 +++++
>  include/stdlib.h         |  3 ---
>  malloc/arena.c           | 12 ++----------
>  malloc/hooks.c           |  3 +++
>  malloc/malloc-internal.h |  5 +++++
>  malloc/malloc.c          |  4 +---
>  malloc/malloc.h          |  8 --------
>  malloc/morecore.c        | 15 +++++++++++++--
>  8 files changed, 29 insertions(+), 26 deletions(-)
> 
> diff --git a/NEWS b/NEWS
> index cebe8384bf..2533919f75 100644
> --- a/NEWS
> +++ b/NEWS
> @@ -106,6 +106,11 @@ Deprecated and removed features, and other changes affecting compatibility:
>    legacy programs until they are updated to remove references to the memory
>    allocation hooks.
>  
> +* The __morecore and __after_morecore_hook malloc hooks and the default
> +  implementation __default_morecore have been removed from the API.  Existing
> +  applications will continue to link against these symbols but the interfaces
> +  no longer have any effect on malloc.
> +
>  Changes to build and runtime requirements:
>  
>  * On Linux, the shm_open, sem_open, and related functions now expect the
> diff --git a/include/stdlib.h b/include/stdlib.h
> index 1f6e1508e4..1c6f70b082 100644
> --- a/include/stdlib.h
> +++ b/include/stdlib.h
> @@ -306,9 +306,6 @@ libc_hidden_proto (__qfcvt_r)
>  #  define MB_CUR_MAX (_NL_CURRENT_WORD (LC_CTYPE, _NL_CTYPE_MB_CUR_MAX))
>  # endif
>  
> -extern void *__default_morecore (ptrdiff_t) __THROW;
> -libc_hidden_proto (__default_morecore)
> -
>  struct abort_msg_s
>  {
>    unsigned int size;
> diff --git a/malloc/arena.c b/malloc/arena.c
> index 8591c8ea56..00e8b5a32f 100644
> --- a/malloc/arena.c
> +++ b/malloc/arena.c
> @@ -272,14 +272,6 @@ next_env_entry (char ***position)
>  #endif
>  
>  
> -#if defined(SHARED) || defined(USE_MTAG)
> -static void *
> -__failing_morecore (ptrdiff_t d)
> -{
> -  return (void *) MORECORE_FAILURE;
> -}
> -#endif
> -
>  #ifdef SHARED
>  extern struct dl_open_hook *_dl_open_hook;
>  libc_hidden_proto (_dl_open_hook);
> @@ -300,7 +292,7 @@ ptmalloc_init (void)
>  	 and that morecore does not support tagged regions, then
>  	 disable it.  */
>        if (__MTAG_SBRK_UNTAGGED)
> -	__morecore = __failing_morecore;
> +	__always_fail_morecore = true;
>  
>        mtag_enabled = true;
>        mtag_mmap_flags = __MTAG_MMAP_FLAGS;
> @@ -313,7 +305,7 @@ ptmalloc_init (void)
>       generic sbrk implementation also enforces this, but it is not
>       used on Hurd.  */
>    if (!__libc_initial)
> -    __morecore = __failing_morecore;
> +    __always_fail_morecore = true;
>  #endif
>  
>    thread_arena = &main_arena;
> diff --git a/malloc/hooks.c b/malloc/hooks.c
> index 5e9355761a..b40696c8b7 100644
> --- a/malloc/hooks.c
> +++ b/malloc/hooks.c
> @@ -81,6 +81,9 @@ compat_symbol (libc, __memalign_hook, __memalign_hook, GLIBC_2_0);
>  void weak_variable (*__after_morecore_hook) (void) = NULL;
>  compat_symbol (libc, __after_morecore_hook, __after_morecore_hook, GLIBC_2_0);
>  
> +void *(*__morecore)(ptrdiff_t);
> +compat_symbol (libc, __morecore, __morecore, GLIBC_2_0);
> +
>  /* These hooks will get executed only through the interposed allocator
>     functions in libmalloc_compathooks.  This means that the calls to malloc,
>     realloc, etc. will lead back into the interposed functions, which is what we
> diff --git a/malloc/malloc-internal.h b/malloc/malloc-internal.h
> index ee0f5697af..b104f7cdbf 100644
> --- a/malloc/malloc-internal.h
> +++ b/malloc/malloc-internal.h
> @@ -21,6 +21,7 @@
>  
>  #include <malloc-machine.h>
>  #include <malloc-sysdep.h>
> +#include <stdbool.h>
>  
>  /* INTERNAL_SIZE_T is the word-size used for internal bookkeeping of
>     chunk sizes.
> @@ -63,6 +64,8 @@
>  
>  #define top(ar_ptr) ((ar_ptr)->top)
>  
> +extern bool __always_fail_morecore attribute_hidden;
> +
>  /* Called in the parent process before a fork.  */
>  void __malloc_fork_lock_parent (void) attribute_hidden;
>  
> @@ -78,4 +81,6 @@ void __malloc_arena_thread_freeres (void) attribute_hidden;
>  /* Activate a standard set of debugging hooks. */
>  void __malloc_check_init (void) attribute_hidden;
>  
> +extern void *__glibc_morecore (ptrdiff_t) attribute_hidden;
> +
>  #endif /* _MALLOC_INTERNAL_H */
> diff --git a/malloc/malloc.c b/malloc/malloc.c
> index 296e4f9789..79855e93ab 100644
> --- a/malloc/malloc.c
> +++ b/malloc/malloc.c
> @@ -382,10 +382,8 @@ __malloc_assert (const char *assertion, const char *file, unsigned int line,
>  
>  
>  /* Definition for getting more memory from the OS.  */
> -#define MORECORE         (*__morecore)
> +#define MORECORE         (*__glibc_morecore)
>  #define MORECORE_FAILURE 0
> -void * __default_morecore (ptrdiff_t);
> -void *(*__morecore)(ptrdiff_t) = __default_morecore;
>  
>  /* Memory tagging.  */
>  
> diff --git a/malloc/malloc.h b/malloc/malloc.h
> index d066a05d82..2df0b38050 100644
> --- a/malloc/malloc.h
> +++ b/malloc/malloc.h
> @@ -76,14 +76,6 @@ extern void *valloc (size_t __size) __THROW __attribute_malloc__
>  extern void *pvalloc (size_t __size) __THROW __attribute_malloc__
>    __wur __attr_dealloc_free;
>  
> -/* Underlying allocation function; successive calls should return
> -   contiguous pieces of memory.  */
> -extern void *(*__morecore) (ptrdiff_t __size) __MALLOC_DEPRECATED;
> -
> -/* Default value of `__morecore'.  */
> -extern void *__default_morecore (ptrdiff_t __size)
> -__THROW __attribute_malloc__  __MALLOC_DEPRECATED;
> -
>  /* SVID2/XPG mallinfo structure */
>  
>  struct mallinfo
> diff --git a/malloc/morecore.c b/malloc/morecore.c
> index 047228779b..c85a85c0eb 100644
> --- a/malloc/morecore.c
> +++ b/malloc/morecore.c
> @@ -38,16 +38,27 @@ libc_hidden_proto (__sbrk)
>  # define NULL 0
>  #endif
>  
> +#if defined(SHARED) || defined(USE_MTAG)
> +bool __always_fail_morecore = false;
> +#endif
> +
>  /* Allocate INCREMENT more bytes of data space,
>     and return the start of data space, or NULL on errors.
>     If INCREMENT is negative, shrink data space.  */
>  void *
> -__default_morecore (ptrdiff_t increment)
> +__glibc_morecore (ptrdiff_t increment)
>  {
> +#if defined(SHARED) || defined(USE_MTAG)
> +  if (__always_fail_morecore)
> +    return NULL;
> +#endif
> +
>    void *result = (void *) __sbrk (increment);
>    if (result == (void *) -1)
>      return NULL;
>  
>    return result;
>  }
> -libc_hidden_def (__default_morecore)
> +#if SHLIB_COMPAT (libc, GLIBC_2_0, GLIBC_2_34)
> +compat_symbol (libc, __glibc_morecore, __default_morecore, GLIBC_2_0);
> +#endif
> 


-- 
Cheers,
Carlos.