fchdir: simplify error handling, and support dup3

* modules/fchdir (Depends-on): Use strdup-posix, not strdup.  Add
stdbool, malloc-posix, realloc-posix.
* lib/fchdir.c (struct dir_info_t): Delete saved_errno.
(ensure_dirs_slot): Return false on allocation failure.
(rpl_dup2): Delete.
(_gl_register_dup): New function.
(_gl_unregister_fd, rpl_opendir, rpl_dup): Update callers.
(_gl_register_fd): Close fd on allocation failure.
* lib/fcntl.in.h (_gl_register_fd): Update signature.
* lib/unistd.in.h (_gl_register_dup) [FCHDIR_REPLACEMENT]: New
prototype.
(rpl_dup2_fchdir): Delete prototype.
* lib/open.c (open): Update caller.
* lib/dup2.c (dup2): Track fchdir metadata.
* lib/dup3.c (dup3): Likewise.
* m4/dup2.m4 (gl_REPLACE_DUP2): New macro.
* m4/fchdir.m4 (gl_FUNC_FCHDIR): Use it.

Signed-off-by: Eric Blake <ebb9@byu.net>

1 files changed, 13 insertions, 3 deletions

diff --git a/lib/dup2.c b/lib/dup2.c
index fb3ffb0df0..a513e5bfea 100644
--- a/lib/dup2.c
+++ b/lib/dup2.c
@@ -70,6 +70,10 @@ rpl_dup2 (int fd, int desired_fd)
   /* Correct a cygwin 1.5.x errno value.  */
   else if (result == -1 && errno == EMFILE)
     errno = EBADF;
+#ifdef FCHDIR_REPLACEMENT
+  if (fd != desired_fd && result == desired_fd)
+    result = _gl_register_dup (fd, desired_fd);
+#endif
   return result;
 }
 
@@ -98,13 +102,19 @@ dupfd (int fd, int desired_fd)
 int
 dup2 (int fd, int desired_fd)
 {
+  int result;
   if (fd == desired_fd)
-    return fd;
+    return fcntl (fd, F_GETFL) < 0 ? -1 : fd;
   close (desired_fd);
 # ifdef F_DUPFD
-  return fcntl (fd, F_DUPFD, desired_fd);
+  result = fcntl (fd, F_DUPFD, desired_fd);
 # else
-  return dupfd (fd, desired_fd);
+  result = dupfd (fd, desired_fd);
 # endif
+#ifdef FCHDIR_REPLACEMENT
+  if (0 <= result)
+    result = _gl_register_dup (fd, desired_fd);
+#endif
+  return result;
 }
 #endif /* !REPLACE_DUP2 */