Changed C_call_scheme to preserve and restore `last_return_code'.

This fixes a bug which manifests as an access violation during GC.

The GC bug happened because the incorrect value of `last_return_code'
left after the recursive interpretation caused a negative stack
segment size to be computed.  When this was boxed as an unsigned value
it became an illegal pointer object.  Note that this manifestation
would not have happened with the new tagging scheme.

diff --git a/v7/src/microcode/utils.c b/v7/src/microcode/utils.c
index 942aa4a1f8a81a00f9b9913cdd89e782be213ef8..b20bd41998b6fe6f11a6245b5dd3542374412f78 100644 (file)
--- a/v7/src/microcode/utils.c
+++ b/v7/src/microcode/utils.c
@@ -1,6 +1,6 @@
 /* -*-C-*-
 
-$Id: utils.c,v 9.64 1993/09/15 01:05:28 gjr Exp $
+$Id: utils.c,v 9.65 1994/09/29 15:54:27 adams Exp $
 
 Copyright (c) 1987-1993 Massachusetts Institute of Technology
 
@@ -1080,6 +1080,7 @@ DEFUN (C_call_scheme, (proc, nargs, argvec),
        AND SCHEME_OBJECT * argvec)
 {
   SCHEME_OBJECT primitive, prim_lexpr, * sp, result;
+  SCHEME_OBJECT * callers_last_return_code;
 
 #ifdef i386
   extern void * C_Frame_Pointer, * C_Stack_Pointer;
@@ -1094,6 +1095,7 @@ DEFUN (C_call_scheme, (proc, nargs, argvec),
   {  
     primitive = (Regs [REGBLOCK_PRIMITIVE]);
     prim_lexpr = (Regs [REGBLOCK_LEXPR_ACTUALS]);
+    callers_last_return_code = last_return_code;
 
     if (! (PRIMITIVE_P (primitive)))
       abort_to_interpreter (ERR_CANNOT_RECURSE);
@@ -1124,6 +1126,7 @@ DEFUN (C_call_scheme, (proc, nargs, argvec),
       signal_error_from_primitive (ERR_STACK_HAS_SLIPPED);
       /*NOTREACHED*/
 
+    last_return_code = callers_last_return_code;
     Regs [REGBLOCK_LEXPR_ACTUALS] = prim_lexpr;
     Regs [REGBLOCK_PRIMITIVE] = primitive;
   }