WARNS=2 fixes.

The remaining problem of converting highly incompatible pointer types
is done by "laundering" the value through a union.

This solves the problem (in my own mind) of how a "const char *" _ever_
actually gets a value in a WARNS=2 world.

2 files changed, 11 insertions, 9 deletions

diff --git a/usr.bin/su/Makefile b/usr.bin/su/Makefile
index ccf6536..7d20843 100644
--- a/usr.bin/su/Makefile
+++ b/usr.bin/su/Makefile
@@ -6,9 +6,7 @@ PROG=	su
 DPADD+= ${LIBUTIL} ${LIBPAM}
 LDADD+= -lutil ${MINUSLPAM}
 
-# Cannot be enabled because of a truly nasty warning/problem
-# concering execv(2)'s second argument.
-#WARNS?=	2
+WARNS?=	2
 
 BINMODE=4555
 INSTALLFLAGS=-fschg
diff --git a/usr.bin/su/su.c b/usr.bin/su/su.c
index 8f03a4c..a5e454a 100644
--- a/usr.bin/su/su.c
+++ b/usr.bin/su/su.c
@@ -114,13 +114,17 @@ main(int argc, char *argv[])
 	struct pam_conv	conv = {misc_conv, NULL};
 	enum tristate	iscsh;
 	login_cap_t	*lc;
+	union {
+		const char	**a;
+		char		* const b[1];
+	} 		np;
 	uid_t		ruid;
 	gid_t		gid;
 	int		asme, ch, asthem, fastlogin, prio, i, setwhat, retcode,
 			statusp, child_pid, child_pgrp, ret_pid;
 	char		*username, *cleanenv, *class, shellbuf[MAXPATHLEN],
 			myhost[MAXHOSTNAMELEN + 1];
-	const char	*p, *user, *shell, *mytty, **nargv, **np;
+	const char	*p, *user, *shell, *mytty, **nargv;
 
 	shell = class = cleanenv = NULL;
 	asme = asthem = fastlogin = statusp = 0;
@@ -165,7 +169,7 @@ main(int argc, char *argv[])
 	nargv[argc + 3] = NULL;
 	for (i = argc; i >= optind; i--)
 		nargv[i + 3] = argv[i];
-	np = &nargv[i + 3];
+	np.a = &nargv[i + 3];
 
 	argv += optind;
 
@@ -378,18 +382,18 @@ main(int argc, char *argv[])
 
 		if (iscsh == YES) {
 			if (fastlogin)
-				*np-- = "-f";
+				*np.a-- = "-f";
 			if (asme)
-				*np-- = "-m";
+				*np.a-- = "-m";
 		}
 		/* csh strips the first character... */
-		*np = asthem ? "-su" : iscsh == YES ? "_su" : "su";
+		*np.a = asthem ? "-su" : iscsh == YES ? "_su" : "su";
 
 		if (ruid != 0)
 			syslog(LOG_NOTICE, "%s to %s%s", username, user,
 			    ontty());
 
-		execv(shell, np);
+		execv(shell, np.b);
 		err(1, "%s", shell);
 	}
 }