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.

2 files changed, 7 insertions, 4 deletions

diff --git a/etc/DEBUG b/etc/DEBUG
index eef67dad500..d5d582902ab 100644
--- a/etc/DEBUG
+++ b/etc/DEBUG
@@ -144,8 +144,8 @@ These are displayed as integer values (or structures, if you used the
 "--enable-check-lisp-object-type" option at configure time) that are
 hard to interpret, especially if they represent long lists.  You can
 use the 'pp' command to display them in their Lisp form.  That command
-displays its output on the standard error stream (on GNU/Linux, you
-can redirect that to a file using "M-x redirect-debugging-output").
+displays its output on the standard error stream, which you
+can redirect to a file using "M-x redirect-debugging-output".
 This means that if you attach GDB to a running Emacs that was invoked
 from a desktop icon, chances are you will not see the output at all,
 or it will wind up in an obscure place (check the documentation of
@@ -250,8 +250,8 @@ To see the current value of a Lisp Variable, use 'pv variable'.
 These commands send their output to stderr; if that is closed or
 redirected to some file you don't know, you won't see their output.
 This is particularly so for Emacs invoked on MS-Windows from the
-desktop shortcut.  On GNU/Linux, you can use the command
-'redirect-debugging-output' to redirect stderr to a file.
+desktop shortcut.  You can use the command 'redirect-debugging-output'
+to redirect stderr to a file.
 
 Note: It is not a good idea to try 'pr', 'pp', or 'pv' if you know that Emacs
 is in deep trouble: its stack smashed (e.g., if it encountered SIGSEGV
diff --git a/etc/NEWS b/etc/NEWS
index 6ef196aa802..e6b18bff2ec 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -208,6 +208,9 @@ permanent and documented, and may be used by Lisp programs.  Its value
 is a list of currently open parenthesis positions, starting with the
 outermost parenthesis.
 
+** The function 'redirect-debugging-output' now works on platforms
+other than GNU/Linux.
+
 
 * Changes in Emacs 25.2 on Non-Free Operating Systems