[PATCH 5/4] ptsname_r: use instead of ptsname

[Eric Blake]

We might as well be ready for thread-safety, if ptsname_r is
improved to add appropriate locking.

* lib/openpty.c (openpty): Convert for thread-safety.
* lib/unlockpt.c (unlockpt): Likewise.
* modules/openpty (Depends-on): Add ptsname_r.
* modules/unlockpt (Depends-on): Likewise.
* lib/pt_chown.c (do_pt_chown): Document safety.

Signed-off-by: Eric Blake <address@hidden>
---

Again, I'll wait for feedback before pushing this (in part
because right now ptsname_r fails on platforms where the
existing use of ptsname succeeds, while we debate about
making ptsname_r be implemented as a lock around ptsname).

 ChangeLog        |    7 +++++++
 lib/openpty.c    |    5 ++---
 lib/pt_chown.c   |    3 ++-
 lib/unlockpt.c   |    4 ++--
 modules/openpty  |    1 +
 modules/unlockpt |    2 +-
 6 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 404b95d..6cc7e22 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,12 @@
 2011-11-09  Eric Blake  <address@hidden>

+       ptsname_r: use instead of ptsname
+       * lib/openpty.c (openpty): Convert for thread-safety.
+       * lib/unlockpt.c (unlockpt): Likewise.
+       * modules/openpty (Depends-on): Add ptsname_r.
+       * modules/unlockpt (Depends-on): Likewise.
+       * lib/pt_chown.c (do_pt_chown): Document safety.
+
        ptsname_r-tests: new test module
        * modules/ptsname_r-tests: New module.
        * tests/test-ptsname_r.c: New file.
diff --git a/lib/openpty.c b/lib/openpty.c
index d9d9773..5fb5df3 100644
--- a/lib/openpty.c
+++ b/lib/openpty.c
@@ -64,7 +64,7 @@ openpty (int *amaster, int *aslave, char *name,
          struct termios const *termp, struct winsize const *winp)
 {
   int master;
-  char *slave_name;
+  char slave_name[256];
   int slave;

 # if HAVE__GETPTY /* IRIX */
@@ -93,8 +93,7 @@ openpty (int *amaster, int *aslave, char *name,
     goto fail;

 # if !HAVE__GETPTY /* !IRIX */
-  slave_name = ptsname (master);
-  if (slave_name == NULL)
+  if (ptsname_r (master, slave_name, sizeof slave_name))
     goto fail;
 # endif

diff --git a/lib/pt_chown.c b/lib/pt_chown.c
index ccc04fd..bbefe29 100644
--- a/lib/pt_chown.c
+++ b/lib/pt_chown.c
@@ -41,7 +41,8 @@ do_pt_chown (void)
   struct group *p;
   gid_t gid;

-  /* Check that PTY_FILENO is a valid master pseudo terminal.  */
+  /* Check that PTY_FILENO is a valid master pseudo terminal.
+     pt_chown is single-threaded, so no need to drag in ptsname_r.  */
   pty = ptsname (PTY_FILENO);
   if (pty == NULL)
     return errno == EBADF ? FAIL_EBADF : FAIL_EINVAL;
diff --git a/lib/unlockpt.c b/lib/unlockpt.c
index 6785487..f8abd68 100644
--- a/lib/unlockpt.c
+++ b/lib/unlockpt.c
@@ -30,8 +30,8 @@ unlockpt (int fd)
 #if HAVE_REVOKE
   /* MacOS X 10.3, OpenBSD 3.8 do not have the unlockpt function, but they
      have revoke().  */
-  char *name = ptsname (fd);
-  if (name == NULL)
+  char name[256];
+  if (ptsname_r (fd, name, sizeof name))
     return -1;
   return revoke (name);
 #else
diff --git a/modules/openpty b/modules/openpty
index 8d174da..0f99664 100644
--- a/modules/openpty
+++ b/modules/openpty
@@ -10,6 +10,7 @@ pty
 extensions
 fcntl-h         [test $HAVE_OPENPTY = 0 || test $REPLACE_OPENPTY = 1]
 posix_openpt    [test $HAVE_OPENPTY = 0 || test $REPLACE_OPENPTY = 1]
+ptsname_r       [test $HAVE_OPENPTY = 0 || test $REPLACE_OPENPTY = 1]
 ioctl           [test $HAVE_OPENPTY = 0 || test $REPLACE_OPENPTY = 1]

 configure.ac:
diff --git a/modules/unlockpt b/modules/unlockpt
index c917964..063b575 100644
--- a/modules/unlockpt
+++ b/modules/unlockpt
@@ -10,7 +10,7 @@ Depends-on:
 stdlib
 extensions
 fcntl-h         [test $HAVE_UNLOCKPT = 0]
-ptsname         [test $HAVE_UNLOCKPT = 0]
+ptsname_r       [test $HAVE_UNLOCKPT = 0]

 configure.ac:
 gl_FUNC_UNLOCKPT
-- 
1.7.4.4