bin/55527: incorrect output when -k is used and there are more patterns than matches

[silas_netbsd_gnats%nocafe.net@localhost]

>Number:         55527
>Category:       bin
>Synopsis:       incorrect output when -k is used and there are more patterns than matches
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    bin-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri Jul 31 16:35:00 +0000 2020
>Originator:     silas_netbsd_gnats%nocafe.net@localhost
>Release:        NetBSD 8.2
>Organization:
>Environment:
>Description:
When csplit -k flag (which does not remove created files) and there are more
patterns than matches for a file, the file created before the last one has
incorrect output.

Although I'm using NetBSD 8.2, I tested CVS version (1.7) and the behaviour is
the same.
>How-To-Repeat:
cd /tmp
echo '
a:
b:
c:
d:' > test
csplit -k test '/.*:/' '{999}'

# File xx03 should have "c:" but it has "c:\nd:"
>Fix:

The following patch fix that, but I'm not familiar enough with the codebase to
be sure it doesn't break in other situation.
	
--- csplit.c.orig	2020-07-31 12:29:24.234981477 -0300
+++ csplit.c	2020-07-31 12:33:11.423349708 -0300
@@ -410,8 +410,10 @@
 		first = 0;
 	}
 
-	if (p == NULL)
+	if (p == NULL) {
+		toomuch(ofp, 1);
 		errx(1, "%s: no match", re);
+	}
 
 	if (ofs <= 0) {
 		/*