Make file descriptors close-on-exec when possible.

This simplifies Emacs a bit, since it no longer needs to worry
about closing file descriptors by hand in some cases.
It also fixes some unlikely races.  Not all such races, as
libraries often open files internally without setting
close-on-exec, but it's an improvement.
* admin/merge-gnulib (GNULIB_MODULES): Add fcntl, pipe2.
(GNULIB_TOOL_FLAGS): Avoid binary-io, close.  Do not avoid fcntl.
* configure.ac (mkostemp): New function to check for.
(PTY_OPEN): Pass O_CLOEXEC to posix_openpt.
* lib/fcntl.c, lib/getdtablesize.c, lib/pipe2.c, m4/fcntl.m4:
* m4/getdtablesize.m4, m4/pipe2.m4: New files, taken from gnulib.
* lib/gnulib.mk, m4/gnulib-comp.m4: Regenerate.
* nt/gnulib.mk: Remove empty gl_GNULIB_ENABLED_verify section;
otherwise, gnulib-tool complains given close-on-exec changes.
* nt/inc/ms-w32.h (pipe): Remove.
* nt/mingw-cfg.site (ac_cv_func_fcntl, gl_cv_func_fcntl_f_dupfd_cloexec)
(gl_cv_func_fcntl_f_dupfd_works, ac_cv_func_pipe2): New vars.
* src/alloc.c (valid_pointer_p) [!WINDOWSNT]:
* src/callproc.c (Fcall_process) [!MSDOS]:
* src/emacs.c (main) [!DOS_NT]:
* src/nsterm.m (ns_term_init):
* src/process.c (create_process):
Use 'pipe2' with O_CLOEXEC instead of 'pipe'.
* src/emacs.c (Fcall_process_region) [HAVE_MKOSTEMP]:
* src/filelock.c (create_lock_file) [HAVE_MKOSTEMP]:
Prefer mkostemp with O_CLOEXEC to mkstemp.
* src/callproc.c (relocate_fd) [!WINDOWSNT]:
* src/emacs.c (main): Use F_DUPFD_CLOEXEC, not plain F_DUPFD.
No need to use fcntl (..., F_SETFD, FD_CLOEXEC), since we're
now using pipe2.
* src/filelock.c (create_lock_file) [! HAVE_MKOSTEMP]:
Make the resulting file descriptor close-on-exec.
* src/lisp.h, src/lread.c, src/process.c (close_load_descs, close_process_descs):
* src/lread.c (load_descriptor_list, load_descriptor_unwind):
Remove; no longer needed.  All uses removed.
* src/process.c (SOCK_CLOEXEC): Define to 0 if not supplied by system.
(close_on_exec, accept4, process_socket) [!SOCK_CLOEXEC]:
New functions.
(socket) [!SOCK_CLOEXEC]: Supply a substitute.
(Fmake_network_process, Fnetwork_interface_list):
(Fnetwork_interface_info, server_accept_connection):
Make newly-created socket close-on-exec.
* src/sysdep.c (emacs_open, emacs_fopen):
Make new-created descriptor close-on-exec.
* src/w32.c (fcntl): Support F_DUPFD_CLOEXEC well enough for Emacs.
* src/w32.c, src/w32.h (pipe2): Rename from 'pipe', with new flags arg.

Fixes: debbugs:14803

2 files changed, 10 insertions, 4 deletions

diff --git a/admin/ChangeLog b/admin/ChangeLog
index 592a41968db..f7d7cbb55d2 100644
--- a/admin/ChangeLog
+++ b/admin/ChangeLog
@@ -1,3 +1,9 @@
+2013-07-07  Paul Eggert  <eggert@cs.ucla.edu>
+
+        Make file descriptors close-on-exec when possible (Bug#14803).
+        * merge-gnulib (GNULIB_MODULES): Add fcntl, pipe2.
+        (GNULIB_TOOL_FLAGS): Avoid binary-io, close.  Do not avoid fcntl.
+
 2013-07-06  Glenn Morris  <rgm@gnu.org>
 
         * admin.el (manual-misc-manuals): New function.
diff --git a/admin/merge-gnulib b/admin/merge-gnulib
index c8bfe0dacc3..f89fe7959fd 100755
--- a/admin/merge-gnulib
+++ b/admin/merge-gnulib
@@ -29,11 +29,11 @@ GNULIB_MODULES='
   alloca-opt c-ctype c-strcase
   careadlinkat close-stream crypto/md5 crypto/sha1 crypto/sha256 crypto/sha512
   dtoastr dtotimespec dup2 environ execinfo faccessat
-  fcntl-h fdatasync fdopendir filemode fstatat fsync
+  fcntl fcntl-h fdatasync fdopendir filemode fstatat fsync
   getloadavg getopt-gnu gettime gettimeofday
   ignore-value intprops largefile lstat
   manywarnings memrchr mktime
-  pselect pthread_sigmask putenv qacl readlink readlinkat
+  pipe2 pselect pthread_sigmask putenv qacl readlink readlinkat
   sig2str socklen stat-time stdalign stdarg stdbool stdio
   strftime strtoimax strtoumax symlink sys_stat
   sys_time time timer-time timespec-add timespec-sub unsetenv utimens
@@ -41,8 +41,8 @@ GNULIB_MODULES='
 '
 
 GNULIB_TOOL_FLAGS='
-  --avoid=dup
-  --avoid=fchdir --avoid=fcntl --avoid=fstat
+  --avoid=binary-io --avoid=close --avoid=dup
+  --avoid=fchdir --avoid=fstat
   --avoid=malloc-posix --avoid=msvc-inval --avoid=msvc-nothrow
   --avoid=open --avoid=openat-die --avoid=opendir
   --avoid=raise