[v5,8/8] Remove __morecore and __default_morecore

Message ID 20210705170814.4132997-9-siddhesh@sourceware.org
State Superseded
Headers show
Series
  • malloc hooks removal
Related show

Commit Message

Noah Goldstein via Libc-alpha July 5, 2021, 5:08 p.m.
Make the __morecore and __default_morecore symbols compat-only and
remove their declarations from the API.
---
 NEWS                     |  5 +++++
 include/stdlib.h         |  3 ---
 malloc/arena.c           | 12 ++----------
 malloc/hooks.c           |  2 ++
 malloc/malloc-internal.h |  5 +++++
 malloc/malloc.c          |  4 +---
 malloc/malloc.h          |  8 --------
 malloc/morecore.c        | 15 +++++++++++++--
 8 files changed, 28 insertions(+), 26 deletions(-)

-- 
2.31.1

Patch

diff --git a/NEWS b/NEWS
index 4fd4ff0e90..038420a621 100644
--- a/NEWS
+++ b/NEWS
@@ -113,6 +113,11 @@  Deprecated and removed features, and other changes affecting compatibility:
   future release of the GNU C Library.  Users may port away from these hooks by
   writing and preloading their own malloc interposition library.
 
+* 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 1ae57f43d5..0650b05c79 100644
--- a/malloc/arena.c
+++ b/malloc/arena.c
@@ -266,14 +266,6 @@  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);
@@ -294,7 +286,7 @@  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;
@@ -307,7 +299,7 @@  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 50ea03b562..360e4920d1 100644
--- a/malloc/hooks.c
+++ b/malloc/hooks.c
@@ -46,6 +46,8 @@  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);
 
 /* 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
diff --git a/malloc/malloc-internal.h b/malloc/malloc-internal.h
index 258f29584e..611aa97762 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.
@@ -62,6 +63,8 @@ 
 #define MALLOC_ALIGN_MASK (MALLOC_ALIGNMENT - 1)
 
 
+extern bool __always_fail_morecore attribute_hidden;
+
 /* Called in the parent process before a fork.  */
 void __malloc_fork_lock_parent (void) attribute_hidden;
 
@@ -77,4 +80,6 @@  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 00fcc676a0..0b8c6d9086 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