* lib/commonio.c: Avoid PATH_MAX. On glibc, we can use realpath

with a NULL argument.
	* src/useradd.c: Replace PATH_MAX by a fixed constant. The buffer
	was not meant as a storage for a path.
	* src/useradd.c, src/newusers.c, src/chpasswd.c: Better detection
	of fgets errors. Lines shall end with a \n, unless we reached the
	end of file.
	* libmisc/copydir.c: Avoid PATH_MAX. Support file paths with any
	length. Added readlink_malloc().

src/chpasswd.c

@@ -434,11 +434,13 @@ int main (int argc, char **argv)
 		if (NULL != cp) {
 			*cp = '\0';
 		} else {
-			fprintf (stderr,
-			         _("%s: line %d: line too long\n"),
-			         Prog, line);
-			errors++;
-			continue;
+			if (feof (stdin) == 0) {
+				fprintf (stderr,
+				         _("%s: line %d: line too long\n"),
+				         Prog, line);
+				errors++;
+				continue;
+			}
 		}
 
 		/*

src/newusers.c

@@ -863,10 +863,13 @@ int main (int argc, char **argv)
 		if (NULL != cp) {
 			*cp = '\0';
 		} else {
-			fprintf (stderr, _("%s: line %d: line too long\n"),
-			         Prog, line);
-			errors++;
-			continue;
+			if (feof (stdin) == 0) {
+				fprintf (stderr,
+				         _("%s: line %d: line too long\n"),
+				         Prog, line);
+				errors++;
+				continue;
+			}
 		}
 
 		/*

src/useradd.c

@@ -421,7 +421,7 @@ static int set_defaults (void)
 {
 	FILE *ifp;
 	FILE *ofp;
-	char buf[PATH_MAX];
+	char buf[1024];
 	static char new_file[] = NEW_USER_FILE;
 	char *cp;
 	int ofd;
@@ -468,6 +468,16 @@ static int set_defaults (void)
 		cp = strrchr (buf, '\n');
 		if (NULL != cp) {
 			*cp = '\0';
+		} else {
+			/* A line which does not end with \n is only valid
+			 * at the end of the file.
+			 */
+			if (feof (ifp) == 0) {
+				fprintf (stderr,
+				         _("%s: line too long in %s: %s..."),
+				         Prog, def_file, buf);
+				return -1;
+			}
 		}
 
 		if (!out_group && MATCH (buf, DGROUP)) {