Make INTERP_TUI's default ui_out the INTERP_CONSOLE ui_out

[gdb] Make INTERP_TUI's default ui_out the INTERP_CONSOLE ui_out

When calling the bt command using a user-defined command while logging with
redirect (escaping '#' using '\' for git commit message convenience):
...
$ gdb -q a.out
Reading symbols from a.out...
(gdb) define mybt
Type commands for definition of "mybt".
End with a line saying just "end".
>bt
>end
(gdb) set logging redirect on
(gdb) set logging on
Redirecting output to gdb.txt.
Copying debug output to gdb.txt.
(gdb) start
(gdb) mybt
\#0  main () at hello.c:9
...
we get the bt output (the '#0  main () at hello.c:9' above) in the gdb
output rather than in the log file gdb.txt:
...
$ cat gdb.txt
Temporary breakpoint 1 at 0x40053b: file hello.c, line 9.
Starting program: /data/gdb_versions/devel/a.out

Temporary breakpoint 1, main () at hello.c:9
9         printf ("hello\n");
...

If we do the same using "bt" instead of "mybt", the output does end up in the
log file, and not in the gdb output, as expected.

Also, if we build gdb with --disable-tui, the problem disappears.

The problem is caused by:
- the fact that INTERP_TUI maintains two ui_outs, one for TUI mode disabled
  (called the default ui_out) and one for TUI mode enabled, combined with
- the fact that the user-defined commands are interpreted by INTERP_CONSOLE,
  which has its own ui_out.

With --disable-tui, the main interpreter is INTERP_CONSOLE, so the logging
redirect is setup for INTERP_CONSOLE's ui_out, and the redirect has effect
when interpreting the mybt command.

With --enable-tui, the main interpreter is INTERP_TUI, so the logging
redirect is setup for INTERP_TUI's default ui_out, and the redirect has no
effect when interpreting the mybt command using INTERP_CONSOLE.

Fix this by making INTERP_TUI's default ui_out the console ui_out.

Tested on x86_64-linux.

gdb/ChangeLog:

2019-09-05  Tom de Vries  <tdevries@suse.de>

	PR gdb/24956
	* tui/tui-io.c (tui_initialize_io): Make default ui_out the console
	ui_out.

gdb/testsuite/ChangeLog:

2019-09-05  Tom de Vries  <tdevries@suse.de>

	PR gdb/24956
	* gdb.base/ui-redirect.exp: Test output of user-defined command.

---
 gdb/testsuite/gdb.base/ui-redirect.exp | 21 +++++++++++++++++++++
 gdb/tui/tui-io.c                       |  5 ++++-
 2 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/gdb/testsuite/gdb.base/ui-redirect.exp b/gdb/testsuite/gdb.base/ui-redirect.exp
index efcac14b7c..932c74af4b 100644
--- a/gdb/testsuite/gdb.base/ui-redirect.exp
+++ b/gdb/testsuite/gdb.base/ui-redirect.exp
@@ -57,6 +57,24 @@  set cmds "$cmds\n"
 set outdir [standard_output_file {}]
 set cmds_file "$outdir/cmds.txt"
 
+with_test_prefix "userdefined" {
+    set test "define userdefined"
+    gdb_test_multiple $test $test {
+	-re "End with a line saying just \"end\"\\.\r\n>$" {
+	    pass $test
+	}
+    }
+
+    set test "bt"
+    gdb_test_multiple $test $test {
+	-re "\r\n>$" {
+	    pass $test
+	}
+    }
+
+    gdb_test_no_output "end"
+}
+
 with_test_prefix "logging" {
     gdb_test_no_output "set logging file /dev/null"
     gdb_test "set logging on" \
@@ -64,6 +82,7 @@  with_test_prefix "logging" {
     gdb_test "save breakpoints $cmds_file" "Saved to file '$cmds_file'\\." \
 	"save breakpoints cmds.txt"
     cmp_file_string "$cmds_file" "$cmds" "cmds.txt"
+    gdb_test "userdefined" "#0  main ().*"
     gdb_test "set logging off" "Done logging to /dev/null\\."
     gdb_test "help" "List of classes of commands:.*"
 }
@@ -74,6 +93,7 @@  with_test_prefix "redirect" {
     "Redirecting output to /dev/null.*Copying debug output to /dev/null\\."
     gdb_test_no_output "save breakpoints $cmds_file" "save breakpoints cmds.txt"
     cmp_file_string "$cmds_file" "$cmds" "cmds.txt"
+    gdb_test_no_output "userdefined"
     gdb_test "set logging off" "Done logging to /dev/null\\."
     gdb_test "help" "List of classes of commands:.*"
 }
@@ -87,6 +107,7 @@  with_test_prefix "redirect while already logging" {
     gdb_test "save breakpoints $cmds_file" "Saved to file '$cmds_file'\\." \
 	"save breakpoints cmds.txt"
     cmp_file_string "$cmds_file" "$cmds" "cmds.txt"
+    gdb_test "userdefined" "#0  main ().*"
     gdb_test "set logging off" "Done logging to /dev/null\\."
     gdb_test "help" "List of classes of commands:.*"
     gdb_test_no_output "set logging redirect off"
diff --git a/gdb/tui/tui-io.c b/gdb/tui/tui-io.c
index ee581a2ff6..eab894325a 100644
--- a/gdb/tui/tui-io.c
+++ b/gdb/tui/tui-io.c
@@ -43,6 +43,7 @@ 
 #include "gdbsupport/filestuff.h"
 #include "completer.h"
 #include "gdb_curses.h"
+#include "interps.h"
 #include <map>
 
 /* This redefines CTRL if it is not already defined, so it must come
@@ -870,7 +871,9 @@  tui_initialize_io (void)
   tui_out = tui_out_new (tui_stdout);
 
   /* Create the default UI.  */
-  tui_old_uiout = cli_out_new (gdb_stdout);
+  struct interp *interp = interp_lookup (current_ui, "console");
+  tui_old_uiout = dynamic_cast<cli_ui_out *> (interp->interp_ui_out());
+  gdb_assert (tui_old_uiout != nullptr);
 
 #ifdef TUI_USE_PIPE_FOR_READLINE
   /* Temporary solution for readline writing to stdout: redirect