bin/59293: install(1) leaves temp files if interrupted

[campbell+netbsd%mumble.net@localhost]

>Number:         59293
>Category:       bin
>Synopsis:       install(1) leaves temp files if interrupted
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    bin-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Apr 13 22:40:00 +0000 2025
>Originator:     Taylor R Campbell
>Release:        current, 10, 9, ...
>Organization:
The NetBSD Installati^C
>Environment:
>Description:
If install(1) is interrupted, it doesn't do anything to clean up its temp files, which can lead to checkflist failures in builds later:

=======  1 extra files in DESTDIR  =========
Files in DESTDIR but missing from flist.
File is obsolete or flist is out of date ?
------------------------------------------
./usr/include/evrpc.h.inst.UBsDVi
=========  end of 1 extra files  ===========

>How-To-Repeat:
1. install a bunch of files
2. ^C
3. check for *.inst.* temp files
>Fix:
Something like this:

static const char *cleanuppath;
static void
onsignal(int signo)
{
	int errno_save = errno;

	if (cleanuppath != NULL)
		(void)unlink(cleanuppath);

	errno = errno_save;
}

...
+	sigset_t mask, omask;
+
 	(void)snprintf(tmpl, sizeof(tmpl), "%s.inst.XXXXXX", to_name);
+	sigemptyset(&mask);
+	sigaddset(&mask, SIGHUP);
+	sigaddset(&mask, SIGINT);
+	sigaddset(&mask, SIGTERM);
+	sigprocmask(SIG_BLOCK, &mask, &omask);
	if (mktemp(tmpl) == NLL)
		err(EXIT_FAILURE, "%s: mktemp", tmpl);
+	cleanuppath = tmpl;
+	sigprocmask(SIG_SETMASK, &omask, NULL);
	ret = link(from_name, tmpl);
	...
+	sigprocmask(SIG_BLOCK, &mask, &omask);
+	cleanuppath = NULL;
+	sigprocmask(SIG_SETMASK, &omask, NULL);