(scm_must_realloc): bugfix: do mtrigger before

realloc. Thanks to Sam Hocevar for reporting this bug

NEWS

@@ -16,6 +16,12 @@ Changes since Guile 1.6.4 (i.e. changes for 1.6.5):
 
 * Changes to the distribution
 * Changes to the stand-alone interpreter
+
+** GC bug fixed.
+
+The use of scm_must_realloc() for memory which is scanned by GC, could
+trigger a GC scan of a free()d block of memory. This is now fixed.
+
 * Changes to Scheme functions and syntax
 
 ** SRFI-1 delete equality argument order fixed.

THANKS

@@ -46,6 +46,7 @@ For fixes or providing information which led to a fix:
            Eric Hanchrow
 	Utz-Uwe Haus
         Karl M. Hegbloom
+            Sam Hocevar
 	 Anders Holst
          Stefan Jahn
       Steven G. Johnson

libguile/ChangeLog

@@ -1,3 +1,8 @@
+2003-07-17  Han-Wen Nienhuys  <hanwen@cs.uu.nl>
+
+	* gc.c (scm_must_realloc): bugfix: do mtrigger before
+	realloc. Thanks to Sam Hocevar for reporting this bug
+
 2003-06-10  Marius Vollmer  <mvo@zagadka.de>
 
 	* gc_os_dep.c (scm_get_stack_base): New version using

libguile/gc.c

@@ -2051,10 +2051,15 @@ scm_must_realloc (void *where,
     scm_must_free() won't take NULL.
   */
   scm_mallocated += size - old_size;
-  SCM_SYSCALL (ptr = realloc (where, size));
 
+  /*
+    The realloc must be after check_mtrigger(), since realloc might
+    munge the old block of memory, which will be scanned by GC.
+   */
   check_mtrigger (what);
   
+  SCM_SYSCALL (ptr = realloc (where, size));
+
   if (NULL != ptr)
     {
 #ifdef GUILE_DEBUG_MALLOC