* callproc.c (child_setup): Rewrite to avoid two strlen calls.

src/ChangeLog

 2011-06-19  Paul Eggert  <eggert@cs.ucla.edu>
 
+	* callproc.c (child_setup): Rewrite to avoid two strlen calls.
+
 	* process.c (Fformat_network_address): Use EMACS_INT, not EMACS_UINT.
 	We prefer signed integers, even for size calculations.
 

src/callproc.c

@@ -1230,8 +1230,7 @@ child_setup (int in, int out, int err, register char **new_argv, int set_pgrp, L
 
     if (STRINGP (display))
       {
-	int vlen = strlen ("DISPLAY=") + strlen (SSDATA (display)) + 1;
-	char *vdata = (char *) alloca (vlen);
+	char *vdata = (char *) alloca (sizeof "DISPLAY=" + SBYTES (display));
 	strcpy (vdata, "DISPLAY=");
 	strcat (vdata, SSDATA (display));
 	new_env = add_env (env, new_env, vdata);