[src/trunk]: src/usr.bin/make make(1): fix off-by-one error in :C modifier

[rillig <rillig%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/547824673d4c
branches:  trunk
changeset: 936134:547824673d4c
user:      rillig <rillig%NetBSD.org@localhost>
date:      Sun Jul 19 19:27:08 2020 +0000

description:
make(1): fix off-by-one error in :C modifier

Previously this off-by-one error had invoked undefined behavior.
Until today there was no corresponding unit test though.

diffstat:

 usr.bin/make/unit-tests/modmisc.exp |  8 ++++++++
 usr.bin/make/var.c                  |  8 ++++----
 2 files changed, 12 insertions(+), 4 deletions(-)

diffs (60 lines):

diff -r f006718d94ba -r 547824673d4c usr.bin/make/unit-tests/modmisc.exp
--- a/usr.bin/make/unit-tests/modmisc.exp       Sun Jul 19 18:35:53 2020 +0000
+++ b/usr.bin/make/unit-tests/modmisc.exp       Sun Jul 19 19:27:08 2020 +0000
@@ -52,6 +52,10 @@
 mod-loop-dollar:$$5$$:
 mod-loop-dollar:$$${word}$$:
 mod-C-limits:00-ok:1 2323 45456
+make: No subexpression \1
+make: No subexpression \1
+make: No subexpression \1
+make: No subexpression \1
 mod-C-limits:11-missing:1 6
 mod-C-limits:11-ok:1 22 446
 make: No subexpression \2
@@ -59,6 +63,10 @@
 make: No subexpression \2
 make: No subexpression \2
 mod-C-limits:22-missing:1 6
+make: No subexpression \2
+make: No subexpression \2
+make: No subexpression \2
+make: No subexpression \2
 mod-C-limits:22-missing:1 6
 mod-C-limits:22-ok:1 33 556
 exit status 0
diff -r f006718d94ba -r 547824673d4c usr.bin/make/var.c
--- a/usr.bin/make/var.c        Sun Jul 19 18:35:53 2020 +0000
+++ b/usr.bin/make/var.c        Sun Jul 19 19:27:08 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: var.c,v 1.270 2020/07/19 18:35:53 rillig Exp $ */
+/*     $NetBSD: var.c,v 1.271 2020/07/19 19:27:08 rillig Exp $ */
 
 /*
  * Copyright (c) 1988, 1989, 1990, 1993
@@ -69,14 +69,14 @@
  */
 
 #ifndef MAKE_NATIVE
-static char rcsid[] = "$NetBSD: var.c,v 1.270 2020/07/19 18:35:53 rillig Exp $";
+static char rcsid[] = "$NetBSD: var.c,v 1.271 2020/07/19 19:27:08 rillig Exp $";
 #else
 #include <sys/cdefs.h>
 #ifndef lint
 #if 0
 static char sccsid[] = "@(#)var.c      8.3 (Berkeley) 3/19/94";
 #else
-__RCSID("$NetBSD: var.c,v 1.270 2020/07/19 18:35:53 rillig Exp $");
+__RCSID("$NetBSD: var.c,v 1.271 2020/07/19 19:27:08 rillig Exp $");
 #endif
 #endif /* not lint */
 #endif
@@ -1578,7 +1578,7 @@
                    rp++;
                }
 
-               if (n > pat->nsub) {
+               if (n >= pat->nsub) {
                    Error("No subexpression %s", &errstr[0]);
                    subbuf = "";
                    sublen = 0;