Call NULL by its name

In variadic functions we still do the cast.  In POSIX, it's not
necessary, since NULL is required to be of type 'void *', and 'void *'
is guaranteed to have the same alignment and representation as 'char *'.
However, since ISO C still doesn't mandate that, and moreover they're
doing dubious stuff by adding nullptr, let's be on the cautious side.
Also, C++ requires that NULL is _not_ 'void *', but either plain 0 or
some magic stuff.

Signed-off-by: Alejandro Colomar <alx@kernel.org>

libmisc/age.c

@@ -112,7 +112,7 @@ int expire (const struct passwd *pw, /*@null@*/const struct spwd *sp)
 			_exit (126);
 		}
 
-		(void) execl (PASSWD_PROGRAM, PASSWD_PROGRAM, pw->pw_name, (char *) 0);
+		(void) execl (PASSWD_PROGRAM, PASSWD_PROGRAM, pw->pw_name, (char *) NULL);
 		err = errno;
 		perror ("Can't execute " PASSWD_PROGRAM);
 		_exit ((ENOENT == err) ? E_CMD_NOTFOUND : E_CMD_NOEXEC);
@@ -139,7 +139,7 @@ int expire (const struct passwd *pw, /*@null@*/const struct spwd *sp)
 
 void agecheck (/*@null@*/const struct spwd *sp)
 {
-	long now = (long) time ((time_t *) 0) / SCALE;
+	long now = (long) time(NULL) / SCALE;
 	long remain;
 
 	if (NULL == sp) {

libmisc/entry.c

@@ -24,7 +24,7 @@ void pw_entry (const char *name, struct passwd *pwent)
 	struct spwd *spwd;
 
 	if (!(passwd = getpwnam (name))) { /* local, no need for xgetpwnam */
-		pwent->pw_name = (char *) 0;
+		pwent->pw_name = NULL;
 		return;
 	} else {
 		pwent->pw_name = xstrdup (passwd->pw_name);

libmisc/env.c

@@ -41,7 +41,7 @@ static const char *const forbid[] = {
 	"PATH=",
 	"SHELL=",
 	"SHLIB_PATH=",
-	(char *) 0
+	NULL
 };
 
 /* these are allowed, but with no slashes inside
@@ -50,7 +50,7 @@ static const char *const noslash[] = {
 	"LANG=",
 	"LANGUAGE=",
 	"LC_",			/* anything with the LC_ prefix */
-	(char *) 0
+	NULL
 };
 
 /*

libmisc/isexpired.c

@@ -40,7 +40,7 @@ int isexpired (const struct passwd *pw, /*@null@*/const struct spwd *sp)
 {
 	long now;
 
-	now = (long) time ((time_t *) 0) / SCALE;
+	now = (long) time(NULL) / SCALE;
 
 	if (NULL == sp) {
 		return 0;

libmisc/list.c

@@ -33,7 +33,7 @@
 	 * pointer if it is present.
 	 */
 
-	for (i = 0; list[i] != (char *) 0; i++) {
+	for (i = 0; list[i] != NULL; i++) {
 		if (strcmp (list[i], member) == 0) {
 			return list;
 		}
@@ -52,12 +52,12 @@
 	 * is returned to the invoker.
 	 */
 
-	for (i = 0; list[i] != (char *) 0; i++) {
+	for (i = 0; list[i] != NULL; i++) {
 		tmp[i] = list[i];
 	}
 
 	tmp[i] = xstrdup (member);
-	tmp[i+1] = (char *) 0;
+	tmp[i+1] = NULL;
 
 	return tmp;
 }
@@ -83,7 +83,7 @@
 	 * pointer if it is not present.
 	 */
 
-	for (i = j = 0; list[i] != (char *) 0; i++) {
+	for (i = j = 0; list[i] != NULL; i++) {
 		if (strcmp (list[i], member) != 0) {
 			j++;
 		}
@@ -106,14 +106,14 @@
 	 * is returned to the invoker.
 	 */
 
-	for (i = j = 0; list[i] != (char *) 0; i++) {
+	for (i = j = 0; list[i] != NULL; i++) {
 		if (strcmp (list[i], member) != 0) {
 			tmp[j] = list[i];
 			j++;
 		}
 	}
 
-	tmp[j] = (char *) 0;
+	tmp[j] = NULL;
 
 	return tmp;
 }
@@ -142,7 +142,7 @@
 		list++;
 	}
 
-	tmp[i] = (char *) 0;
+	tmp[i] = NULL;
 	return tmp;
 }
 
@@ -217,7 +217,7 @@ bool is_on_list (char *const *list, const char *member)
 	 */
 
 	if ('\0' == *members) {
-		*array = (char *) 0;
+		*array = NULL;
 		free (members);
 		return array;
 	}
@@ -235,7 +235,7 @@ bool is_on_list (char *const *list, const char *member)
 			cp2++;
 			cp = cp2;
 		} else {
-			array[i + 1] = (char *) 0;
+			array[i + 1] = NULL;
 			break;
 		}
 	}

libmisc/loginprompt.c

@@ -122,7 +122,7 @@ void login_prompt (const char *prompt, char *name, int namesize)
 		int envc;
 
 		for (envc = 0; envc < MAX_ENV; envc++) {
-			nvar = strtok ((0 != envc) ? (char *) 0 : cp, " \t,");
+			nvar = strtok ((0 != envc) ? NULL : cp, " \t,");
 			if (NULL == nvar) {
 				break;
 			}

libmisc/pwdcheck.c

@@ -26,7 +26,7 @@ void passwd_check (const char *user, const char *passwd, unused const char *prog
 	if (NULL != sp) {
 		passwd = sp->sp_pwdp;
 	}
-	if (pw_auth (passwd, user, PW_LOGIN, (char *) 0) != 0) {
+	if (pw_auth (passwd, user, PW_LOGIN, NULL) != 0) {
 		SYSLOG ((LOG_WARN, "incorrect password for `%s'", user));
 		(void) sleep (1);
 		fprintf (log_get_logfd(), _("Incorrect password for %s.\n"), user);

libmisc/shell.c

@@ -33,7 +33,7 @@ int shell (const char *file, /*@null@*/const char *arg, char *const envp[])
 	char arg0[1024];
 	int err;
 
-	if (file == (char *) 0) {
+	if (file == NULL) {
 		errno = EINVAL;
 		return errno;
 	}
@@ -44,7 +44,7 @@ int shell (const char *file, /*@null@*/const char *arg, char *const envp[])
 	 * that.  So, we determine the 0'th entry only if they
 	 * don't want to tell us what it is themselves.
 	 */
-	if (arg == (char *) 0) {
+	if (arg == NULL) {
 		(void) snprintf (arg0, sizeof arg0, "-%s", Basename (file));
 		arg0[sizeof arg0 - 1] = '\0';
 		arg = arg0;
@@ -55,7 +55,7 @@ int shell (const char *file, /*@null@*/const char *arg, char *const envp[])
 	 * able to figure out what we are up to without too much
 	 * grief.
 	 */
-	(void) execle (file, arg, (char *) 0, envp);
+	(void) execle (file, arg, (char *) NULL, envp);
 	err = errno;
 
 	if (access (file, R_OK|X_OK) == 0) {
@@ -63,7 +63,7 @@ int shell (const char *file, /*@null@*/const char *arg, char *const envp[])
 		 * Assume this is a shell script (with no shebang).
 		 * Interpret it with /bin/sh
 		 */
-		(void) execle (SHELL, "sh", "-", file, (char *)0, envp);
+		(void) execle (SHELL, "sh", "-", file, (char *) NULL, envp);
 		err = errno;
 	}
 

libmisc/sulog.c

@@ -64,7 +64,7 @@ void sulog (const char *tty, bool success, const char *oldname, const char *name
 		/* Do not return if the group permission were raised. */
 		exit (EXIT_FAILURE);
 	}
-	if (fp == (FILE *) 0) {
+	if (fp == NULL) {
 		return;		/* can't open or create logfile */
 	}