gww@beatnix.UUCP (Gary Winiger) (03/13/88)
Subject: Vi can longjmp before setjmp is called. +Fix
Index: ucb/ex/ex.h 4.3BSD +Fix
Description:
It is possible for vi to take a longjmp before the setjmp has
completed.
Repeat-By:
The macro CATCH (defined in ex.h) sets a flag to tell if the
the jump buffer is valid. At least in fastpeekkey() (ex_vget.c)
the signal can be user generated (SIGINT). With the original
version of CATCH the flag is set before the setjmp is called,
thus with a lot of good luck, one could enter the signal handler
(trapalarm()) before the setjmp.
By inspection of CATCH in ex.h.
Fix:
The attached code solves this problem at Elxsi.
Gary..
{ucbvax!sun,lll-lcc!lll-tis,amdahl!altos86,bridge2}!elxsi!gww
--------- cut --------- snip --------- :.,$w diff -------------
Index: ucb/ex/ex.h
*** /tmp/,RCSt1003323 Tue Sep 22 16:42:41 1987
--- ex.h Tue Sep 22 16:39:02 1987
***************
*** 1,6 ****
! /* $Header: ex.h,v 1.1 86/12/23 18:15:35 gww Exp $ ENIX BSD
*
* $Log: ex.h,v $
* Revision 1.1 86/12/23 18:15:35 gww
* Initial revision
*
--- 1,10 ----
! /* $Header: ex.h,v 1.2 87/09/22 16:37:57 gww Exp $ ENIX BSD
*
* $Log: ex.h,v $
+ * Revision 1.2 87/09/22 16:37:57 gww
+ * Guard against possible timing bug. If a signal comes before the setjmp has
+ * been executed. (This version of the fix by corbett.)
+ *
* Revision 1.1 86/12/23 18:15:35 gww
* Initial revision
*
***************
*** 259,266 ****
#define setlastchar(c) lastc = c
#define ungetchar(c) peekc = c
! #define CATCH vcatch = 1; if (setjmp(vreslab) == 0) {
! #define ONERR } else { vcatch = 0;
#define ENDCATCH } vcatch = 0;
/*
--- 263,270 ----
#define setlastchar(c) lastc = c
#define ungetchar(c) peekc = c
! #define CATCH if (vcatch = !setjmp(vreslab)) {
! #define ONERR } else {
#define ENDCATCH } vcatch = 0;
/*