Subject: Re: bug#554: OSX: with-temp-buffer kills unrelated processes

From: Markus Triska <[email-masked]>
Date: Wed, 16 Jul 2008 17:27:47 +0200

YAMAMOTO Mitsuharu <[email-masked]> writes:

> OK, close-on-exec seems to be usable for the `fork' case.  How about
> the patch below?

Thank you very much; I've tested the following adapted version of your
patch with the latest CVS trunk of Emacs, and the problem seems gone.

All the best,
Markus

diff --git a/src/callproc.c b/src/callproc.c
index a6de766..3d61e64 100644
--- a/src/callproc.c
+++ b/src/callproc.c
@@ -1047,8 +1047,8 @@ add_env (char **env, char **new_env, char *string)
    Therefore, the superior process must save and restore the value
    of environ around the vfork and the call to this function.
 
-   SET_PGRP is nonzero if we should put the subprocess into a separate
-   process group.
+   RET_ON_FAIL is nonzero if we should return from the function on
+   failure of execvp rather than calling _exit.
 
    CURRENT_DIR is an elisp string giving the path of the current
    directory the subprocess should have.  Since we can't really signal
@@ -1056,10 +1056,10 @@ add_env (char **env, char **new_env, char *string)
    executable directory by the parent.  */
 
 int
-child_setup (in, out, err, new_argv, set_pgrp, current_dir)
+child_setup (in, out, err, new_argv, ret_on_fail, current_dir)
      int in, out, err;
      register char **new_argv;
-     int set_pgrp;
+     int ret_on_fail;
      Lisp_Object current_dir;
 {
   char **env;
@@ -1291,7 +1291,8 @@ child_setup (in, out, err, new_argv, set_pgrp, current_dir)
   emacs_write (1, "Can't exec program: ", 20);
   emacs_write (1, new_argv[0], strlen (new_argv[0]));
   emacs_write (1, "\n", 1);
-  _exit (1);
+  if (!ret_on_fail)
+    _exit (1);
 #endif /* not WINDOWSNT */
 #endif /* not MSDOS */
 }
diff --git a/src/process.c b/src/process.c
index c82584a..b0bebeb 100644
--- a/src/process.c
+++ b/src/process.c
@@ -1851,6 +1851,9 @@ create_process (process, new_argv, current_dir)
   int inchannel, outchannel;
   pid_t pid;
   int sv[2];
+#if !defined (WINDOWSNT) && defined (FD_CLOEXEC)
+  int wait_child_setup[2];
+#endif
 #ifdef POSIX_SIGNALS
   sigset_t procmask;
   sigset_t blocked;
@@ -1893,12 +1896,6 @@ create_process (process, new_argv, current_dir)
 #endif
       if (forkin < 0)
 	report_file_error ("Opening pty", Qnil);
-#if defined (DONT_REOPEN_PTY)
-      /* In the case that vfork is defined as fork, the parent process
-	 (Emacs) may send some data before the child process completes
-	 tty options setup.  So we setup tty before forking.  */
-      child_setup_tty (forkout);
-#endif /* DONT_REOPEN_PTY */
 #else
       forkin = forkout = -1;
 #endif /* not USG, or USG_SUBTTY_WORKS */
@@ -1924,6 +1921,25 @@ create_process (process, new_argv, current_dir)
       forkin = sv[0];
     }
 
+#if !defined (WINDOWSNT) && defined (FD_CLOEXEC)
+    {
+      int tem;
+
+      tem = pipe (wait_child_setup);
+      if (tem < 0)
+	report_file_error ("Creating pipe", Qnil);
+      tem = fcntl (wait_child_setup[1], F_GETFD, 0);
+      if (tem >= 0)
+	tem = fcntl (wait_child_setup[1], F_SETFD, tem | FD_CLOEXEC);
+      if (tem < 0)
+	{
+	  emacs_close (wait_child_setup[0]);
+	  emacs_close (wait_child_setup[1]);
+	  report_file_error ("Setting file descriptor flags", Qnil);
+	}
+    }
+#endif
+
 #if 0
   /* Replaced by close_process_descs */
   set_exclusive_use (inchannel);
@@ -2150,16 +2166,21 @@ create_process (process, new_argv, current_dir)
 #endif /* SIGCHLD */
 #endif /* !POSIX_SIGNALS */
 
-#if !defined (DONT_REOPEN_PTY)
 	if (pty_flag)
 	  child_setup_tty (xforkout);
-#endif /* not DONT_REOPEN_PTY */
 #ifdef WINDOWSNT
 	pid = child_setup (xforkin, xforkout, xforkout,
 			   new_argv, 1, current_dir);
 #else  /* not WINDOWSNT */
+#ifdef FD_CLOEXEC
+	emacs_close (wait_child_setup[0]);
+#endif
 	child_setup (xforkin, xforkout, xforkout,
 		     new_argv, 1, current_dir);
+#ifdef FD_CLOEXEC
+	emacs_close (wait_child_setup[0]);
+#endif
+	_exit (1);
 #endif /* not WINDOWSNT */
       }
     environ = save_environ;
@@ -2211,6 +2232,21 @@ create_process (process, new_argv, current_dir)
       else
 #endif
 	XPROCESS (process)->tty_name = Qnil;
+
+#if !defined (WINDOWSNT) && defined (FD_CLOEXEC)
+      /* Wait for child_setup to complete in case that vfork is
+	 actually defined as fork.  The descriptor wait_child_setup[1]
+	 of a pipe is closed at the child side either by close-on-exec
+	 on successful execvp or by the explicit emacs_close call
+	 before _exit above.  */
+      {
+	char dummy;
+
+	emacs_close (wait_child_setup[1]);
+	emacs_read (wait_child_setup[0], &dummy, 1);
+	emacs_close (wait_child_setup[0]);
+      }
+#endif
     }
 
   /* Restore the signal state whether vfork succeeded or not.