eh-common.h (struct eh_context): Add comment for hidden use of field dynamic_handler_chain.

       * eh-common.h (struct eh_context): Add comment for hidden use of
        field dynamic_handler_chain.
        * except.c (get_dynamic_handler_chain): Comment on, and use the
        correct offset of the dynamic_handler_chain field.

From-SVN: r20540

gcc/ChangeLog

+Wed Jun 17 15:57:48 EDT 1998  Andrew MacLeod  (amacleod@cygnus.com)
+
+	* eh-common.h (struct eh_context): Add comment for hidden use of
+	field dynamic_handler_chain.
+	* except.c (get_dynamic_handler_chain): Comment on, and use the
+	correct offset of the dynamic_handler_chain field.
+
 1998-06-17 12:46:56 1998  Jim Wilson  <wilson@cygnus.com>
 
 	* mips/iris6.h (LINK_SPEC): Add -woff 131.

gcc/eh-common.h

@@ -20,7 +20,10 @@
 
 /* The handler_label field MUST be the first field in this structure. The 
    __throw()  library routine expects uses __eh_stub() from except.c, which
-   simply dereferences the context pointer to get the handler */
+   simply dereferences the context pointer to get the handler.
+   The routine get_dynamic_handler_chain() also has a dependancy on
+   the location of 'dynamic_handler_chain'. If its location is changed, 
+   that routine must be modified as well. */
 
 struct eh_context
 {

gcc/except.c

@@ -1017,7 +1017,10 @@ get_dynamic_handler_chain ()
   rtx ehc, dhc, result;
 
   ehc = get_eh_context ();
-  dhc = ehc;
+
+  /* This is the offset of dynamic_handler_chain in the eh_context struct
+     declared in eh-common.h. If its location is change, change this offset */
+  dhc = plus_constant (ehc, GET_MODE_SIZE (Pmode));
 
   result = copy_to_reg (dhc);