Provide more POSIX-complaint ttyname_r(3) interface[1], which is slightly

different from what has been offered in libc_r (the one spotted in the
original PR which is found in libthr has already been removed by David's
commit, which is rev. 1.44 of lib/libthr/thread/thr_private.h):
	- Use POSIX standard prototype for ttyname_r, which is,
		int ttyname_r(int, char *, size_t);
	  Instead of:
	  	char *ttyname_r(int, char *, size_t);
	  This is to conform IEEE Std 1003.1, 2004 Edition [1].
	- Since we need to use standard errno for return code, include
	  errno.h in ttyname.c
	- Update ttyname(3) implementation according to reflect the API
	  change.
	- Document new ttyname_r(3) behavior
	- Since we already make use of a thread local storage for
	  ttyname(3), remove the BUGS section.
	- Remove conflicting ttyname_r related declarations found in libc_r.

Hopefully this change should not have changed the API/ABI, as the ttyname_r
symbol was never introduced before the last unistd.h change which happens a
couple of days before.

[1] http://www.opengroup.org/onlinepubs/009695399/functions/ttyname.html

Requested by:	Tom McLaughlin <tmclaugh sdf lonestar org>
Through PR:	threads/76938
Patched by:	Craig Rodrigues <rodrigc crodrigues org> (with minor changes)
Prompted by:	mezz@

2 files changed, 41 insertions, 22 deletions

diff --git a/lib/libc/gen/ttyname.3 b/lib/libc/gen/ttyname.3
index dcea14a..db67314 100644
--- a/lib/libc/gen/ttyname.3
+++ b/lib/libc/gen/ttyname.3
@@ -32,11 +32,12 @@
 .\"     @(#)ttyname.3	8.1 (Berkeley) 6/4/93
 .\" $FreeBSD$
 .\"
-.Dd June 4, 1993
+.Dd May 14, 2005
 .Dt TTYNAME 3
 .Os
 .Sh NAME
 .Nm ttyname ,
+.Nm ttyname_r ,
 .Nm isatty ,
 .Nm ttyslot
 .Nd get name of associated terminal (tty) from file descriptor
@@ -46,7 +47,7 @@
 .In unistd.h
 .Ft char *
 .Fn ttyname "int fd"
-.Ft char *
+.Ft int
 .Fn ttyname_r "int fd" "char *buf" "size_t len"
 .Ft int
 .Fn isatty "int fd"
@@ -82,7 +83,13 @@ function
 gets the related device name of
 a file descriptor for which
 .Fn isatty
-is true
+is true.
+.Pp
+.Fn ttyname
+returns the name stored in a static buffer which will be overwritten
+on subsequent calls.
+.Fn ttyname_r
+takes a buffer and length as arguments to avoid this problem.
 .Pp
 The
 .Fn ttyslot
@@ -100,12 +107,25 @@ is true; otherwise
 a
 .Dv NULL
 pointer is returned.
+The
+.Fn ttyname_r
+function returns 0 if successful.  Otherwise an error number is returned.
 .Pp
 The
 .Fn ttyslot
 function
 returns the unit number of the device file if found; otherwise
 the value zero is returned.
+.Sh ERRORS
+.Fn ttyname_r
+may return the following error codes:
+.Bl -tag -width Er
+.It Bq Er ENOTTY
+.Fa fd
+is not a valid file descriptor.
+.It Bq Er ERANGE
+.Fa bufsize
+is smaller than the length of the string to be returned.
 .Sh FILES
 .Bl -tag -width /etc/ttys -compact
 .It Pa /dev/\(**
@@ -123,11 +143,6 @@ and
 function
 appeared in
 .At v7 .
-.Sh BUGS
-The
-.Fn ttyname
-function leaves its result in an internal static object and returns
-a pointer to that object.
-Subsequent calls to
-.Fn ttyname
-will modify the same object.
+.Fn ttyname_r
+appeared in
+.Fx 6.0 .
diff --git a/lib/libc/gen/ttyname.c b/lib/libc/gen/ttyname.c
index 5630442..54bc24b 100644
--- a/lib/libc/gen/ttyname.c
+++ b/lib/libc/gen/ttyname.c
@@ -50,6 +50,7 @@ __FBSDID("$FreeBSD$");
 #include <string.h>
 #include <paths.h>
 #include <pthread.h>
+#include <errno.h>
 #include "un-namespace.h"
 
 #include "libc_private.h"
@@ -60,34 +61,32 @@ static pthread_mutex_t	ttyname_lock = PTHREAD_MUTEX_INITIALIZER;
 static pthread_key_t	ttyname_key;
 static int		ttyname_init = 0;
 
-char *
+int
 ttyname_r(int fd, char *buf, size_t len)
 {
 	struct stat	sb;
-	char		*rval;
 	struct fiodgname_arg fgn;
 
-	rval = NULL;
 	*buf = '\0';
 
 	/* Must be a terminal. */
 	if (!isatty(fd))
-		return (rval);
+		return (ENOTTY);
 	/* Must be a character device. */
 	if (_fstat(fd, &sb) || !S_ISCHR(sb.st_mode))
-		return (rval);
+		return (ENOTTY);
 	/* Must have enough room */
 	if (len <= sizeof(_PATH_DEV))
-		return (rval);
+		return (ERANGE);
 
 	strcpy(buf, _PATH_DEV);
 	fgn.len = len - strlen(buf);
 	fgn.buf = buf + strlen(buf);
 	if (!_ioctl(fd, FIODGNAME, &fgn))
-		return(buf);
+		return (EINVAL);
 	devname_r(sb.st_rdev, S_IFCHR,
 	    buf + strlen(buf), sizeof(buf) - strlen(buf));
-	return (buf);
+	return (0);
 }
 
 char *
@@ -95,8 +94,12 @@ ttyname(int fd)
 {
 	char	*buf;
 
-	if (__isthreaded == 0)
-		return (ttyname_r(fd, ttyname_buf, sizeof ttyname_buf));
+	if (__isthreaded == 0) {
+		if (ttyname_r(fd, ttyname_buf, sizeof ttyname_buf) != 0)
+			return (NULL);
+		else
+			return (ttyname_buf);
+	}
 
 	if (ttyname_init == 0) {
 		_pthread_mutex_lock(&ttyname_lock);
@@ -121,6 +124,7 @@ ttyname(int fd)
 			return (NULL);
 		}
 	}
-	return (ttyname_r(fd, buf, sizeof(_PATH_DEV) + MAXNAMLEN));
+	ttyname_r(fd, buf, sizeof(_PATH_DEV) + MAXNAMLEN);
+	return (buf);
 }