microcode: Fix sense of subtraction so STACK_CHECK does anything.

(cherry picked from commit c692f84195254b00af8260e44e99e65eea3fda57)

diff --git a/src/microcode/hooks.c b/src/microcode/hooks.c
index 4c3c97116d760288e7030f2e11f5623704902b8f..78ce28d57bd41e7499c865fb2ad4a0ad1d94580a 100644 (file)
--- a/src/microcode/hooks.c
+++ b/src/microcode/hooks.c
@@ -265,7 +265,7 @@ unpack_control_point (SCHEME_OBJECT cp)
 
     stack_pointer = STACK_BOTTOM;
     CLEAR_INTERRUPT (INT_Stack_Overflow);
-    STACK_CHECK (end_from - scan_from);
+    STACK_CHECK (scan_from - end_from);
     
     while (scan_from > end_from)
       STACK_PUSH (*--scan_from);