Enabled TUI mode on MSYS2

[Giah de Barag <gdb at crelg dot com>]

2016-09-13  Giah de Barag  <gdb@crelg.com>


Summary
-------

Here is a patch and a build recipe for GDB on MSYS2 to enable TUI mode.

The current gdb (7.11.1) in MSYS2 does not support TUI mode. However, GDB
TUI mode works fine on MSYS2. It depends upon python, curses, and three
environment variables: PYTHONHOME (/mingw32 or /mingw64) and TERMINFO
(/usr/share/terminfo) and TERM.


Impact
------

This patch only affects builds where (#if defined __MINGW32__) is true.


Explanation of Changes
----------------------

GDB works fine in emacs, in bash, and in mintty. In the Windows Console (start
cmd.exe) TUI mode works also. TUI mode depends upon ncurses and python. Have
them ready before running configure.

Eli Zaretski (https://www.sourceware.org/ml/gdb/2014-12/msg00039.html)
comments that he had to “hide libncurses from the configure script in order to
build a working debugger.” This comment might be dated.

GDB with TUI mode works fine on MSYS2 with curses, with this small patch. I saw
that getch() (which becomes the ncurses getch() when you link in ncurses) in
input.c returns EOF as soon as you hit any character. Fortunately, Windows
conio has deprecated getch() and has defined _getch() in its place. So I
changed it to _getch(), to access the conio version.

There is a tiny issue now that with this conio _getch(), gdb does not properly
process backspace characters.

Not having backspace characters in plain non-TUI mode in the Windows Console
is hardly bothersome, because you can type “tui enable” and have a better
environment. If you have to be in non-TUI mode for some reason, a workaround
is [Ctrl]-[L] to refresh the line. Therefore I am using conio _getch() not
ncurses getch().


Note to GDB Maintainers
-----------------------

Someone with understanding of event handling by gdb, Windows conio, and UNIX
curses: Can you please look where there is “getch()” in rl_getc() in input.c
and see why it returns EOF no matter what (when linking with ncurses). Then do
as I did in this patch and change it to _getch() to access the conio version
and see why backspace characters are not handled properly. They are processed,
but the display is not refreshed, and you have to hit [Ctrl]-[L] to refresh.

Also, this is the first time I am doing something like this, so if I am
neglecting any rule of communication of this list, please inform me, and I
will correct it.


MSYS2 GDB Build Recipe
----------------------

# Steps to produce a (debuggable) gdb with TUI mode support on MSYS2:

# These steps are tested with Server 2008 R2 which is supposed to be
# similar to Windows 7.

# Install MSYS2

# see also http://msys2.github.io

wget http://repo.msys2.org/distrib/msys2-x86-64-latest.exe

# update msys2

pacman --noconfirm -Sy pacman # update pacman (quit mintty and restart)
pacman --noconfirm -Syu       # update package db (quit mintty and restart)
pacman --noconfirm -Su        # update packages (repeat until nothing changes)

# get a bunch of stuff

arch=i686
# OR
arch=x86-64

# These are all the packages I currently use. You probably don’t need all
# these packages, but you definitely need python and curses.

pacman --needed --noconfirm -S base-devel git svn tar zip unzip asciidoc
pacman --needed --noconfirm -S mingw-w64-${arch}-emacs
pacman --needed --noconfirm -S mingw-w64-${arch}-toolchain
pacman --needed --noconfirm -S mingw-w64-${arch}-libxml2
pacman --needed --noconfirm -S mingw-w64-${arch}-gnutls
pacman --needed --noconfirm -S mingw-w64-${arch}-libxslt
pacman --needed --noconfirm -S mingw-w64-${arch}-libjpeg-turbo
pacman --needed --noconfirm -S mingw-w64-${arch}-libtiff
pacman --needed --noconfirm -S mingw-w64-${arch}-giflib
pacman --needed --noconfirm -S mingw-w64-${arch}-icu
pacman --needed --noconfirm -S mingw-w64-${arch}-libsndfile
pacman --needed --noconfirm -S mingw-w64-${arch}-aspell
pacman --needed --noconfirm -S mingw-w64-${arch}-lcms
pacman --needed --noconfirm -S mingw-w64-${arch}-lcms2
pacman --needed --noconfirm -S mingw-w64-${arch}-sqlite3
pacman --needed --noconfirm -S mingw-w64-${arch}-windows-default-manifest 

# Get and build GDB (same version as in MSYS2 pacman)

# see https://www.gnu.org/software/gdb/current/

git clone -b gdb-7.11-branch git://sourceware.org/git/binutils-gdb.git
./configure
make

# Debug GDB with itself. Use existing gdb in emacs to debug the newly-built
# gdb, in tui mode, in a Windows Console. To improve debugging experience,
# modify the CFLAGS that you just used to build GDB.

cd binutils-gdb/gdb
runemacs
M-x gdb
gdb --annotate=0 -i=mi ./gdb
set new-console on
set args -tui
run


Note to MSYS2 Maintainers
-------------------------

Is this enough info for you to be able to build an improved GDB that supports
TUI mode? Or do you need me to refine down the list of packages that has to be
installed before building GDB?


Patches
-------

Attached is patch relative to gdb-7.11-branch. All it does is change getch()
to _getch() in input.c (and remove compiler warnings about implicitly declared
Windows conio functions _kbhit() and _getch()).


----- CUT HERE -----
diff --git a/readline/input.c b/readline/input.c
index 7c74c99..57df227 100644
--- a/readline/input.c
+++ b/readline/input.c
@@ -69,6 +69,10 @@ extern int errno;
 #include "rlshell.h"
 #include "xmalloc.h"
 
+#if defined (__MINGW32__)
+#include <conio.h>
+#endif
+
 /* What kind of non-blocking I/O do we have? */
 #if !defined (O_NDELAY) && defined (O_NONBLOCK)
 #  define O_NDELAY O_NONBLOCK	/* Posix style */
@@ -190,7 +194,7 @@ rl_gather_tyi ()
 #endif
 
   result = -1;
-#if defined (FIONREAD)
+#if defined (FIONREAD) && !defined (__MINGW32__)
   errno = 0;
   result = ioctl (tty, FIONREAD, &chars_avail);
   if (result == -1 && errno == EIO)
@@ -286,7 +290,7 @@ _rl_input_available ()
   fd_set readfds, exceptfds;
   struct timeval timeout;
 #endif
-#if !defined (HAVE_SELECT) && defined(FIONREAD)
+#if !defined (HAVE_SELECT) && defined(FIONREAD) && !defined (__MINGW32__)
   int chars_avail;
 #endif
   int tty;
@@ -303,7 +307,7 @@ _rl_input_available ()
   return (select (tty + 1, &readfds, (fd_set *)NULL, &exceptfds, &timeout) > 0);
 #else
 
-#if defined (FIONREAD)
+#if defined (FIONREAD) && !defined (__MINGW32__)
   if (ioctl (tty, FIONREAD, &chars_avail) == 0)
     return (chars_avail);
 #endif
@@ -466,6 +470,6 @@ rl_getc (stream)
 
 #if defined (__MINGW32__)
       if (isatty (fileno (stream)))
-	return (getch ());
+	return (_getch ()); /* use conio; ncurses makes tui work, but getch() here returns EOF */
 #endif
       result = read (fileno (stream), &c, sizeof (unsigned char));