libutil: take a size_t in trimdomain()

INT_MAX is already larger than a reasonable hostname might be, but
size_t makes some of this easier to reason about as we do arithmetic
with it.  This would maybe not be worth it if we had to bump the
soversion because of it, but libutil does symbol versioning now so we
can provide a compat shim.

While we're here, fix some inconsistencies in argument names in the
manpage.

Reviewed by:	des
Obtained from:	https://github.com/apple-oss-distributions/libutil
Sponsored by:	Klara, Inc.
Differential Revision:	https://reviews.freebsd.org/D54622

lib/libutil/Symbol.map

@@ -115,7 +115,6 @@ FBSD_1.8 {
 	setclassenvironment;
 	setclassresources;
 	setusercontext;
-	trimdomain;
 	uu_lock_txfr;
 	uu_lock;
 	uu_lockerr;
@@ -130,6 +129,10 @@ FBSD_1.8 {
 	crypt_set_format;
 };
 
+FBSD_1.9 {
+	trimdomain;
+};
+
 FBSDprivate_1.0 {
 	__pw_initpwd;
 };

lib/libutil/libutil.h

@@ -140,7 +140,7 @@ int	realhostname(char *_host, size_t _hsize, const struct in_addr *_ip);
 int	realhostname_sa(char *_host, size_t _hsize, struct sockaddr *_addr,
 	    int _addrlen);
 int	_secure_path(const char *_path, uid_t _uid, gid_t _gid);
-void	trimdomain(char *_fullhost, int _hostsize);
+void	trimdomain(char *_fullhost, size_t _hostsize);
 const char *
 	uu_lockerr(int _uu_lockresult);
 int	uu_lock(const char *_ttyname);

lib/libutil/trimdomain.3

@@ -22,7 +22,7 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd February 17, 2025
+.Dd March 3, 2026
 .Dt TRIMDOMAIN 3
 .Os
 .Sh NAME
@@ -34,7 +34,7 @@
 .In sys/types.h
 .In libutil.h
 .Ft void
-.Fn trimdomain "char *fullhost" "int hostsize"
+.Fn trimdomain "char *fullhost" "size_t hostsize"
 .Sh DESCRIPTION
 The function
 .Fn trimdomain
@@ -53,13 +53,13 @@ the first time this function is called and is cached for future use.
 The
 .Fn trimdomain
 function will only trim the domain name if the passed
-.Ar fullname
+.Ar fullhost
 ends with the current domain name and if the length of the resulting host
 name does not exceed
 .Ar hostsize .
 .Pp
 If the passed
-.Ar fullname
+.Ar fullhost
 is actually an X11
 .Ev DISPLAY
 specification of the form

lib/libutil/trimdomain.c

@@ -34,6 +34,7 @@
 #include <string.h>
 #include <unistd.h>
 
+void		freebsd15_trimdomain(char *, int);
 static int	isDISP(const char *);
 
 /*-
@@ -50,7 +51,7 @@ static int	isDISP(const char *);
  *     trimdomain("abcde.my.domain:0.0", 8)   ->   "abcde.my.domain:0.0"
  */
 void
-trimdomain(char *fullhost, int hostsize)
+trimdomain(char *fullhost, size_t hostsize)
 {
 	static size_t dlen;
 	static int first = 1;
@@ -89,6 +90,21 @@ trimdomain(char *fullhost, int hostsize)
 	}
 }
 
+void
+freebsd15_trimdomain(char *fullhost, int hostsize)
+{
+	/*
+	 * Note that we intentionally aren't doing anything here about a
+	 * negative `hostsize`, to preserve historical behavior.  Functionally,
+	 * it would have ended up as a very large size passing to the memchr(3),
+	 * thus either appearing to work or reading off the end of the buffer if
+	 * `fullhost` is actually malformed.
+	 */
+	trimdomain(fullhost, hostsize);
+}
+
+__sym_compat(trimdomain, freebsd15_trimdomain, FBSD_1.8);
+
 /*
  * Is the given string NN or NN.NN where ``NN'' is an all-numeric string ?
  */