Port redirect-debugging-output to non-GNU/Linux

Problem reported by Kylie McClain for musl in:
http://lists.gnu.org/archive/html/emacs-devel/2016-03/msg01592.html
* etc/DEBUG, etc/NEWS: Mention this.
* src/callproc.c (child_setup) [!MSDOS]:
* src/dispnew.c (init_display):
* src/emacs.c (main, Fdaemon_initialized):
* src/minibuf.c (read_minibuf_noninteractive):
* src/regex.c (xmalloc, xrealloc):
Prefer symbolic names like STDERR_FILENO to magic numbers like 2,
to make file-descriptor manipulation easier to follow.
* src/emacs.c (relocate_fd) [!WINDOWSNT]: Remove; no longer needed
now that we make sure stdin, stdout and stderr are open.  All uses
removed.
(main): Make sure standard FDs are OK.  Prefer symbolic names like
EXIT_FAILURE to magic numbers like 1.  Use bool for boolean.
* src/lisp.h (init_standard_fds): New decl.
* src/print.c (WITH_REDIRECT_DEBUGGING_OUTPUT) [GNU_LINUX]:
Remove; no longer needed.
(Fredirect_debugging_output): Define on all platforms, not just
GNU/Linux.  Redirect file descriptor, not stream, so that the code
works even if stderr is not an lvalue.  Report an error if the
file arg is neither a string nor nil.
(syms_of_print): Always define redirect-debugging-output.
* src/sysdep.c (force_open, init_standard_fds): New functions.

1 files changed, 3 insertions, 55 deletions

diff --git a/src/callproc.c b/src/callproc.c
index db602f538c9..8578556b695 100644
--- a/src/callproc.c
+++ b/src/callproc.c
@@ -1078,10 +1078,6 @@ usage: (call-process-region START END PROGRAM &optional DELETE BUFFER DISPLAY &r
   return unbind_to (count, val);
 }
 
-#ifndef WINDOWSNT
-static int relocate_fd (int fd, int minfd);
-#endif
-
 static char **
 add_env (char **env, char **new_env, char *string)
 {
@@ -1310,37 +1306,14 @@ child_setup (int in, int out, int err, char **new_argv, bool set_pgrp,
   return cpid;
 
 #else  /* not WINDOWSNT */
-  /* Make sure that in, out, and err are not actually already in
-     descriptors zero, one, or two; this could happen if Emacs is
-     started with its standard in, out, or error closed, as might
-     happen under X.  */
-  {
-    int oin = in, oout = out;
-
-    /* We have to avoid relocating the same descriptor twice!  */
-
-    in = relocate_fd (in, 3);
-
-    if (out == oin)
-      out = in;
-    else
-      out = relocate_fd (out, 3);
-
-    if (err == oin)
-      err = in;
-    else if (err == oout)
-      err = out;
-    else
-      err = relocate_fd (err, 3);
-  }
 
 #ifndef MSDOS
   /* Redirect file descriptors and clear the close-on-exec flag on the
      redirected ones.  IN, OUT, and ERR are close-on-exec so they
      need not be closed explicitly.  */
-  dup2 (in, 0);
-  dup2 (out, 1);
-  dup2 (err, 2);
+  dup2 (in, STDIN_FILENO);
+  dup2 (out, STDOUT_FILENO);
+  dup2 (err, STDERR_FILENO);
 
   setpgid (0, 0);
   tcsetpgrp (0, pid);
@@ -1359,31 +1332,6 @@ child_setup (int in, int out, int err, char **new_argv, bool set_pgrp,
 #endif  /* not WINDOWSNT */
 }
 
-#ifndef WINDOWSNT
-/* Move the file descriptor FD so that its number is not less than MINFD.
-   If the file descriptor is moved at all, the original is closed on MSDOS,
-   but not elsewhere as the caller will close it anyway.  */
-static int
-relocate_fd (int fd, int minfd)
-{
-  if (fd >= minfd)
-    return fd;
-  else
-    {
-      int new = fcntl (fd, F_DUPFD_CLOEXEC, minfd);
-      if (new == -1)
-        {
-          emacs_perror ("while setting up child");
-          _exit (EXIT_CANCELED);
-        }
-#ifdef MSDOS
-      emacs_close (fd);
-#endif
-      return new;
-    }
-}
-#endif /* not WINDOWSNT */
-
 static bool
 getenv_internal_1 (const char *var, ptrdiff_t varlen, char **value,
                    ptrdiff_t *valuelen, Lisp_Object env)