Fix bug #12774 with crashes in ralloc.c.

 src/ralloc.c (relinquish): If real_morecore fails to return memory
 to the system, don't crash; instead, leave the last heap
 unchanged and return.

diff --git a/src/ChangeLog b/src/ChangeLog
index 3ae755f3d203185879f2889e18f42786af866591..c49039a3cf9afadc7a39dbe52d80765933013d5e 100644 (file)
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,9 @@
+2012-11-05  Eli Zaretskii  <eliz@gnu.org>
+
+       * ralloc.c (relinquish): If real_morecore fails to return memory
+       to the system, don't crash; instead, leave the last heap
+       unchanged and return.  (Bug#12774)
+
 2012-11-03  Eli Zaretskii  <eliz@gnu.org>
 
        * lisp.mk: Adjust comments to the fact that term/internal is now

diff --git a/src/ralloc.c b/src/ralloc.c
index 11897411930355f0e32cec3b2fae905b301b23bb..e5bf76b0e6d63dec768f6a0b723a6d1ca4b26e6f 100644 (file)
--- a/src/ralloc.c
+++ b/src/ralloc.c
@@ -327,6 +327,8 @@ relinquish (void)
 
       if ((char *)last_heap->end - (char *)last_heap->bloc_start <= excess)
        {
+         heap_ptr lh_prev;
+
          /* This heap should have no blocs in it.  If it does, we
             cannot return it to the system.  */
          if (last_heap->first_bloc != NIL_BLOC
@@ -335,28 +337,26 @@ relinquish (void)
 
          /* Return the last heap, with its header, to the system.  */
          excess = (char *)last_heap->end - (char *)last_heap->start;
-         last_heap = last_heap->prev;
-         last_heap->next = NIL_HEAP;
+         lh_prev = last_heap->prev;
+         /* If the system doesn't want that much memory back, leave
+            last_heap unaltered to reflect that.  This can occur if
+            break_value is still within the original data segment.  */
+         if ((*real_morecore) (- excess) != 0)
+           {
+             last_heap = lh_prev;
+             last_heap->next = NIL_HEAP;
+           }
        }
       else
        {
          excess = (char *) last_heap->end
                        - (char *) ROUNDUP ((char *)last_heap->end - excess);
-         last_heap->end = (char *) last_heap->end - excess;
-       }
-
-      if ((*real_morecore) (- excess) == 0)
-       {
-         /* If the system didn't want that much memory back, adjust
-             the end of the last heap to reflect that.  This can occur
-             if break_value is still within the original data segment.  */
-         last_heap->end = (char *) last_heap->end + excess;
-         /* Make sure that the result of the adjustment is accurate.
-             It should be, for the else clause above; the other case,
-             which returns the entire last heap to the system, seems
-             unlikely to trigger this mode of failure.  */
-         if (last_heap->end != (*real_morecore) (0))
-           emacs_abort ();
+         /* If the system doesn't want that much memory back, leave
+            the end of the last heap unchanged to reflect that.  This
+            can occur if break_value is still within the original
+            data segment.  */
+         if ((*real_morecore) (- excess) != 0)
+           last_heap->end = (char *) last_heap->end - excess;
        }
     }
 }