From: Stephen Adams <edu/mit/csail/zurich/adams>
Date: Thu, 29 Sep 1994 15:54:27 +0000 (+0000)
Subject: Changed C_call_scheme to preserve and restore `last_return_code'.
X-Git-Tag: 20090517-FFI~7102
X-Git-Url: https://birchwood-abbey.net/git?a=commitdiff_plain;h=78263d45162f9683625dfa8b11f08d2244e8e52d;p=mit-scheme.git

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 942aa4a1f..b20bd4199 100644
--- 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;
   }