Revert 4248f0da6f.

Objections were raised surrounding the calloc simplification
and it is better to revert the patch, continue discussions
and then submit a new patch for inclusion with all issues
fully addressed.

ChangeLog

@@ -1,3 +1,7 @@
+2014-03-03  Carlos O'Donell  <carlos@redhat.com>
+
+	* malloc/malloc.c (__libc_calloc): Revert last change.
+
 2014-03-03  Adhemerval Zanella  <azanella@linux.vnet.ibm.com>
 
 	* sysdeps/powerpc/fpu/libm-test-ulps: Update.

malloc/malloc.c

@@ -3141,8 +3141,13 @@ __libc_pvalloc (size_t bytes)
 void *
 __libc_calloc (size_t n, size_t elem_size)
 {
-  INTERNAL_SIZE_T bytes;
+  mstate av;
+  mchunkptr oldtop, p;
+  INTERNAL_SIZE_T bytes, sz, csz, oldtopsize;
   void *mem;
+  unsigned long clearsize;
+  unsigned long nclears;
+  INTERNAL_SIZE_T *d;
 
   /* size_t is unsigned so the behavior on overflow is defined.  */
   bytes = n * elem_size;
@@ -3161,15 +3166,113 @@ __libc_calloc (size_t n, size_t elem_size)
     atomic_forced_read (__malloc_hook);
   if (__builtin_expect (hook != NULL, 0))
     {
-      mem = (*hook)(bytes, RETURN_ADDRESS (0));
-    }
-  else
-    mem = __libc_malloc (bytes);
+      sz = bytes;
+      mem = (*hook)(sz, RETURN_ADDRESS (0));
+      if (mem == 0)
+        return 0;
 
-  if (mem == 0)
+      return memset (mem, 0, sz);
+    }
+
+  sz = bytes;
+
+  arena_get (av, sz);
+  if (!av)
     return 0;
 
-  return memset (mem, 0, bytes);
+  /* Check if we hand out the top chunk, in which case there may be no
+     need to clear. */
+#if MORECORE_CLEARS
+  oldtop = top (av);
+  oldtopsize = chunksize (top (av));
+# if MORECORE_CLEARS < 2
+  /* Only newly allocated memory is guaranteed to be cleared.  */
+  if (av == &main_arena &&
+      oldtopsize < mp_.sbrk_base + av->max_system_mem - (char *) oldtop)
+    oldtopsize = (mp_.sbrk_base + av->max_system_mem - (char *) oldtop);
+# endif
+  if (av != &main_arena)
+    {
+      heap_info *heap = heap_for_ptr (oldtop);
+      if (oldtopsize < (char *) heap + heap->mprotect_size - (char *) oldtop)
+        oldtopsize = (char *) heap + heap->mprotect_size - (char *) oldtop;
+    }
+#endif
+  mem = _int_malloc (av, sz);
+
+
+  assert (!mem || chunk_is_mmapped (mem2chunk (mem)) ||
+          av == arena_for_chunk (mem2chunk (mem)));
+
+  if (mem == 0)
+    {
+      LIBC_PROBE (memory_calloc_retry, 1, sz);
+      av = arena_get_retry (av, sz);
+      if (__builtin_expect (av != NULL, 1))
+        {
+          mem = _int_malloc (av, sz);
+          (void) mutex_unlock (&av->mutex);
+        }
+      if (mem == 0)
+        return 0;
+    }
+  else
+    (void) mutex_unlock (&av->mutex);
+  p = mem2chunk (mem);
+
+  /* Two optional cases in which clearing not necessary */
+  if (chunk_is_mmapped (p))
+    {
+      if (__builtin_expect (perturb_byte, 0))
+        return memset (mem, 0, sz);
+
+      return mem;
+    }
+
+  csz = chunksize (p);
+
+#if MORECORE_CLEARS
+  if (perturb_byte == 0 && (p == oldtop && csz > oldtopsize))
+    {
+      /* clear only the bytes from non-freshly-sbrked memory */
+      csz = oldtopsize;
+    }
+#endif
+
+  /* Unroll clear of <= 36 bytes (72 if 8byte sizes).  We know that
+     contents have an odd number of INTERNAL_SIZE_T-sized words;
+     minimally 3.  */
+  d = (INTERNAL_SIZE_T *) mem;
+  clearsize = csz - SIZE_SZ;
+  nclears = clearsize / sizeof (INTERNAL_SIZE_T);
+  assert (nclears >= 3);
+
+  if (nclears > 9)
+    return memset (d, 0, clearsize);
+
+  else
+    {
+      *(d + 0) = 0;
+      *(d + 1) = 0;
+      *(d + 2) = 0;
+      if (nclears > 4)
+        {
+          *(d + 3) = 0;
+          *(d + 4) = 0;
+          if (nclears > 6)
+            {
+              *(d + 5) = 0;
+              *(d + 6) = 0;
+              if (nclears > 8)
+                {
+                  *(d + 7) = 0;
+                  *(d + 8) = 0;
+                }
+            }
+        }
+    }
+
+  return mem;
 }
 
 /*