Update.

	* malloc/obstack.c (_obstack_newchunk): Correctly align first returned
	block.
	* malloc/tst-obstack.c: New file.
	Patch and test case by Alexandre Duret-Lutz <duret_g@epita.fr>.

2 files changed, 64 insertions, 4 deletions

diff --git a/malloc/obstack.c b/malloc/obstack.c
index 38fc02f..6b32678 100644
--- a/malloc/obstack.c
+++ b/malloc/obstack.c
@@ -282,9 +282,10 @@ _obstack_newchunk (h, length)
   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 @@ _obstack_newchunk (h, length)
   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 @@ _obstack_newchunk (h, length)
     {
       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 @@ _obstack_newchunk (h, length)
     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 @@ _obstack_newchunk (h, length)
       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;
diff --git a/malloc/tst-obstack.c b/malloc/tst-obstack.c
new file mode 100644
index 0000000..bd00a0a
--- /dev/null
+++ b/malloc/tst-obstack.c
@@ -0,0 +1,54 @@
+/* Test case by Alexandre Duret-Lutz <duret_g@epita.fr>.  */
+#include <obstack.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#define obstack_chunk_alloc verbose_malloc
+#define obstack_chunk_free verbose_free
+#define ALIGN_BOUNDARY 64
+#define ALIGN_MASK (ALIGN_BOUNDARY - 1)
+#define OBJECT_SIZE 1000
+
+static void *
+verbose_malloc (size_t size)
+{
+  void *buf = malloc (size);
+  printf ("malloc (%u) => %p\n", size, buf);
+  return buf;
+}
+
+static void
+verbose_free (void *buf)
+{
+  free (buf);
+  printf ("free (%p)\n", buf);
+}
+
+int
+main (void)
+{
+  struct obstack obs;
+  int i;
+  int result = 0;
+
+  obstack_init (&obs);
+  obstack_alignment_mask (&obs) = ALIGN_MASK;
+  /* finish an empty object to take alignment into account */
+  obstack_finish (&obs);
+
+  /* let's allocate some objects and print their addresses */
+  for (i = 15; i > 0; --i)
+    {
+      void *obj = obstack_alloc (&obs, OBJECT_SIZE);
+
+      printf ("obstack_alloc (%u) => %p \t%s\n", OBJECT_SIZE, obj,
+	      ((uintptr_t) obj & ALIGN_MASK) ? "(not aligned)" : "");
+      result |= ((uintptr_t) obj & ALIGN_MASK) != 0;
+  }
+
+  /* clean up */
+  obstack_free (&obs, 0);
+
+  return result;
+}