Change the interface of getlogin_r to return an int. The former

interface was based on a draft version of POSIX whereas the final
(1996) version of POSIX specified that the error is returned.

While I'm here, fix getlogin_r so that it works for more than just
the first time it's called.

Reviewed by:	wes, wollman (man page)

lib/libc/gen/getlogin.c

@@ -38,43 +38,76 @@ static char sccsid[] = "@(#)getlogin.c	8.1 (Berkeley) 6/4/93";
 #endif /* LIBC_SCCS and not lint */
 
 #include <sys/param.h>
+#include <errno.h>
 #include <pwd.h>
 #include <utmp.h>
 #include <stdio.h>
 #include <string.h>
 #include <unistd.h>
 
-int	_logname_valid;		/* known to setlogin() */
+#include <libc_private.h>
 
-char *
+#ifndef _THREAD_SAFE
-getlogin()
+#define	THREAD_LOCK()
+#define	THREAD_UNLOCK()
+#else
+#include <pthread.h>
+#include "pthread_private.h"
+static struct pthread_mutex logname_lock = PTHREAD_MUTEX_STATIC_INITIALIZER;
+static pthread_mutex_t logname_mutex = &logname_lock;
+#define	THREAD_LOCK()	if (__isthreaded) pthread_mutex_lock(&logname_mutex)
+#define	THREAD_UNLOCK()	if (__isthreaded) pthread_mutex_unlock(&logname_mutex)
+#endif /* _THREAD_SAFE */
+
+int		_logname_valid;		/* known to setlogin() */
+
+static char *
+getlogin_basic(int *status)
 {
 	static char logname[MAXLOGNAME];
 
 	if (_logname_valid == 0) {
 #ifdef __NETBSD_SYSCALLS
-		if (__getlogin(logname, sizeof(logname) - 1) < 0)
+		if (__getlogin(logname, sizeof(logname) - 1) < 0) {
 #else
-		if (_getlogin(logname, sizeof(logname)) < 0)
+		if (_getlogin(logname, sizeof(logname)) < 0) {
 #endif
-			return ((char *)NULL);
+			*status = errno;
+			return (NULL);
+		}
 		_logname_valid = 1;
 	}
-	return (*logname ? logname : (char *)NULL);
+	*status = 0;
+	return (*logname ? logname : NULL);
 }
 
-
 char *
+getlogin(void)
+{
+	char	*result;
+	int	status;
+
+	THREAD_LOCK();
+	result = getlogin_basic(&status);
+	THREAD_UNLOCK();
+	return (result);
+}
+
+int
 getlogin_r(char *logname, int namelen)
 {
-	if (_logname_valid == 0) {
+	char	*result;
-#ifdef __NETBSD_SYSCALLS
+	int	len;
-		if (__getlogin(logname, namelen - 1) < 0)
+	int	status;
-#else
+	
-		if (_getlogin(logname, namelen) < 0)
+	THREAD_LOCK();
-#endif
+	result = getlogin_basic(&status);
-			return ((char *)NULL);
+	if (status == 0) {
-		_logname_valid = 1;
+		if ((len = strlen(result) + 1) > namelen)
+			status = ERANGE;
+		else
+			strncpy(logname, result, len);
 	}
-	return (*logname ? logname : (char *)NULL);
+	THREAD_UNLOCK();
+	return (status);
 }

lib/libc/sys/getlogin.2

@@ -47,7 +47,7 @@
 .Ft char *
 .Fn getlogin void
 .Fd #include <sys/param.h>
-.Ft char *
+.Ft int
 .Fn getlogin_r "char *name" "int len"
 .Ft int
 .Fn setlogin "const char *name"
@@ -132,12 +132,12 @@ precautions to prevent security violations.
 .Sh RETURN VALUES
 If a call to
 .Fn getlogin
-succeeds, it returns a pointer to a null-terminated string in a static buffer.
+succeeds, it returns a pointer to a null-terminated string in a static buffer,
-.Fn getlogin_r
+or
-returns a pointer to the buffer passed in by the caller on success.
-Both return
 .Dv NULL
 if the name has not been set.
+.Fn getlogin_r
+returns zero if successful, or the error number upon failure.
 .Pp
 If a call to
 .Fn setlogin
@@ -166,6 +166,8 @@ Login names are limited to
 characters, currently 17 including null.
 .It Bq Er EPERM
 The caller tried to set the login name and was not the super-user.
+.It Bq Er ERANGE
+The size of the buffer is smaller than the result to be returned.
 .El
 .Sh SEE ALSO
 .Xr setsid 2 ,
@@ -186,3 +188,14 @@ The
 .Fn getlogin
 function first appeared in
 .Bx 4.4 .
+The return value of
+.Fn getlogin_r
+was changed from earlier versions of FreeBSD to be conformant with
+.St -iso9945-1 .
+.Sh STANDARDS
+.Fn getlogin
+and
+.Fn getlogin_r
+conform to
+.St -iso9945-1 .
+