PATCH: obstack: first object of each chunk not aligned

[Alexandre Duret-Lutz <duret_g at lrde dot epita dot fr>]

As a followup to my bug report, would this be ok ?

Index: ChangeLog
from  Alexandre Duret-Lutz  <duret_g@epita.fr>

	* malloc/obstack.c (_obstack_newchunk): Use alignment_mask to
	align the first object in a new chunk.

Index: malloc/obstack.c
===================================================================
RCS file: /cvs/glibc/libc/malloc/obstack.c,v
retrieving revision 1.10
diff -u -r1.10 obstack.c
--- obstack.c	2000/10/16 16:16:29	1.10
+++ obstack.c	2000/10/23 16:38:29
@@ -282,9 +282,10 @@
   register long obj_size = h->next_free - h->object_base;
   register long i;
   long already;
+  char *object_base;
 
   /* Compute size for new chunk.  */
-  new_size = (obj_size + length) + (obj_size >> 3) + 100;
+  new_size = (obj_size + length) + (obj_size >> 3) + h->alignment_mask + 100;
   if (new_size < h->chunk_size)
     new_size = h->chunk_size;
 
@@ -296,6 +297,11 @@
   new_chunk->prev = old_chunk;
   new_chunk->limit = h->chunk_limit = (char *) new_chunk + new_size;
 
+  /* Compute an aligned object_base in the new chunk */
+  object_base =
+    __INT_TO_PTR ((__PTR_TO_INT (new_chunk->contents) + h->alignment_mask)
+		  & ~ (h->alignment_mask));
+
   /* Move the existing object to the new chunk.
      Word at a time is fast and is safe if the object
      is sufficiently aligned.  */
@@ -303,7 +309,7 @@
     {
       for (i = obj_size / sizeof (COPYING_UNIT) - 1;
 	   i >= 0; i--)
-	((COPYING_UNIT *)new_chunk->contents)[i]
+	((COPYING_UNIT *)object_base)[i]
 	  = ((COPYING_UNIT *)h->object_base)[i];
       /* We used to copy the odd few remaining bytes as one extra COPYING_UNIT,
 	 but that can cross a page boundary on a machine
@@ -314,7 +320,7 @@
     already = 0;
   /* Copy remaining bytes one by one.  */
   for (i = already; i < obj_size; i++)
-    new_chunk->contents[i] = h->object_base[i];
+    object_base[i] = h->object_base[i];
 
   /* If the object just copied was the only data in OLD_CHUNK,
      free that chunk and remove it from the chain.
@@ -325,7 +331,7 @@
       CALL_FREEFUN (h, old_chunk);
     }
 
-  h->object_base = new_chunk->contents;
+  h->object_base = object_base;
   h->next_free = h->object_base + obj_size;
   /* The new chunk certainly contains no empty object yet.  */
   h->maybe_empty_object = 0;

-- 
Alexandre Duret-Lutz