[PATCH 4/4] ptsname_r: work around FreeBSD issue

[Eric Blake]

POSIX does not require ptsname() to set errno on failure, and
FreeBSD 8.2 leaves it unchanged.

* lib/ptsname_r.c (ptsname_r): Guarantee errno on ptsname failure.
* doc/posix-functions/ptsname.texi (ptsname): Document the issue.

Signed-off-by: Eric Blake <address@hidden>
---
 ChangeLog                        |    4 ++++
 doc/posix-functions/ptsname.texi |    3 +++
 lib/ptsname_r.c                  |   14 +++++++++++++-
 3 files changed, 20 insertions(+), 1 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 70172b4..d7326ef 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,9 @@
 2011-11-07  Eric Blake  <address@hidden>

+       ptsname_r: work around FreeBSD issue
+       * lib/ptsname_r.c (ptsname_r): Guarantee errno on ptsname failure.
+       * doc/posix-functions/ptsname.texi (ptsname): Document the issue.
+
        ptsname_r: port to Solaris
        * m4/ptsname_r.m4 (gl_FUNC_PTSNAME_R): Also check for ptsname.
        * m4/ptsname.m4 (gl_FUNC_PTSNAME): Optimize check.
diff --git a/doc/posix-functions/ptsname.texi b/doc/posix-functions/ptsname.texi
index 2584af8..3ad5fc1 100644
--- a/doc/posix-functions/ptsname.texi
+++ b/doc/posix-functions/ptsname.texi
@@ -25,6 +25,9 @@ ptsname
 This function is not thread-safe on some platforms:
 Cygwin 1.7.9.
 Likewise, the gnulib replacement is not thread-safe.
address@hidden
+As allowed by POSIX, this function does not set errno on some platforms:
+FreeBSD 8.2.
 @end itemize

 Note that the Gnulib module @code{ptsname_r} is a version of this
diff --git a/lib/ptsname_r.c b/lib/ptsname_r.c
index e200f34..c4b1c69 100644
--- a/lib/ptsname_r.c
+++ b/lib/ptsname_r.c
@@ -23,6 +23,8 @@

 #if HAVE_PTSNAME

+# include <fcntl.h>
+
 /* Store at most BUFLEN characters of the pathname of the slave pseudo
    terminal associated with the master FD is open on in BUF.
    Return 0 on success, otherwise an error number.  */
@@ -31,15 +33,25 @@ ptsname_r (int fd, char *buf, size_t buflen)
 {
   /* This assumes nothing else directly calls ptsname().  */
   char *name;
+  int saved_errno = errno;

   if (!buf)
     return errno = EINVAL;
+
+  /* Work around FreeBSD 8.2 ptsname(-1) that fails to set errno.  */
+  saved_errno = errno;
+  errno = 0;
   name = ptsname (fd);
   if (!name)
-    return errno;
+    {
+      if (!errno && fcntl (fd, F_GETFL) >= 0)
+        errno = ENOTTY;
+      return errno;
+    }
   if (buflen <= strlen (name))
     return errno = ERANGE;
   strcpy (buf, name);
+  errno = saved_errno;
   return 0;
 }

-- 
1.7.4.4