Fix "layout reg" crash

Commit d7e7473 ("Eliminate make_cleanup_ui_file_delete / make
ui_file a class hierarchy") introduced a problem when using "layout
regs", that leads gdb to crash when issuing:

./gdb ./a.out -ex 'layout regs' -ex start

From the backtrace, it's caused by this 'delete' on tui_restore_gdbout():

 (gdb) bt
 #0  0x00007ffff6b962b2 in free () from /lib64/libc.so.6
 #1  0x000000000059fa47 in tui_restore_gdbout (ui=0x22997b0) at ../../gdb/tui/tui-regs.c:714
 #2  0x0000000000619996 in do_my_cleanups (pmy_chain=pmy_chain@entry=0x1e08320 <cleanup_chain>, old_chain=old_chain@entry=0x235b4b0) at ../../gdb/common/cleanups.c:154
 #3  0x0000000000619b1d in do_cleanups (old_chain=old_chain@entry=0x235b4b0) at ../../gdb/common/cleanups.c:176
 #4  0x000000000059fb0d in tui_register_format (frame=frame@entry=0x22564e0, regnum=regnum@entry=0) at ../../gdb/tui/tui-regs.c:747
 #5  0x000000000059ffeb in tui_get_register (data=0x2434d18, changedp=0x0, regnum=0, frame=0x22564e0) at ../../gdb/tui/tui-regs.c:768
 #6  tui_show_register_group (refresh_values_only=<optimized out>, frame=0x22564e0, group=0x1e09250 <general_group>) at ../../gdb/tui/tui-regs.c:287
 #7  tui_show_registers (group=0x1e09250 <general_group>) at ../../gdb/tui/tui-regs.c:156
 #8  0x00000000005a07cf in tui_check_register_values (frame=frame@entry=0x22564e0) at ../../gdb/tui/tui-regs.c:496
 #9  0x00000000005a3e65 in tui_check_data_values (frame=frame@entry=0x22564e0) at ../../gdb/tui/tui-windata.c:232
 #10 0x000000000059cf65 in tui_refresh_frame_and_register_information (registers_too_p=1) at ../../gdb/tui/tui-hooks.c:156
 #11 0x00000000006d5c05 in generic_observer_notify (args=0x7fffffffdbe0, subject=<optimized out>) at ../../gdb/observer.c:167
 #12 observer_notify_normal_stop (bs=<optimized out>, print_frame=print_frame@entry=1) at ./observer.inc:61
 #13 0x00000000006a6409 in normal_stop () at ../../gdb/infrun.c:8364
 #14 0x00000000006af8f5 in fetch_inferior_event (client_data=<optimized out>) at ../../gdb/infrun.c:3990
 #15 0x000000000066f0fd in gdb_wait_for_event (block=block@entry=0) at ../../gdb/event-loop.c:859
 #16 0x000000000066f237 in gdb_do_one_event () at ../../gdb/event-loop.c:322
 #17 0x000000000066f386 in gdb_do_one_event () at ../../gdb/event-loop.c:353
 #18 0x00000000007411bc in wait_sync_command_done () at ../../gdb/top.c:570
 #19 0x0000000000741426 in maybe_wait_sync_command_done (was_sync=0) at ../../gdb/top.c:587
 #20 execute_command (p=<optimized out>, p@entry=0x7fffffffe43a "start", from_tty=from_tty@entry=1) at ../../gdb/top.c:676
 #21 0x00000000006c2048 in catch_command_errors (command=0x741200 <execute_command(char*, int)>, arg=0x7fffffffe43a "start", from_tty=1) at ../../gdb/main.c:376
 #22 0x00000000006c2b60 in captured_main_1 (context=0x7fffffffde70) at ../../gdb/main.c:1119
 #23 captured_main (data=0x7fffffffde70) at ../../gdb/main.c:1140
 #24 gdb_main (args=args@entry=0x7fffffffdf90) at ../../gdb/main.c:1158
 #25 0x0000000000408cf5 in main (argc=<optimized out>, argv=<optimized out>) at ../../gdb/gdb.c:32
 (gdb) f 1
 #1  0x000000000059fa47 in tui_restore_gdbout (ui=0x22997b0) at ../../gdb/tui/tui-regs.c:714
 714	  delete gdb_stdout;

The problem is simply that the commit mentioned above made the ui_file
that gdb_stdout is temporarily set to be a stack-allocated
string_file, while before it used to be a heap-allocated ui_file.  The
fix is simply to remove the now-incorrect delete.

New test included, which exercises enabling all TUI layouts, with and
without execution.  (This particular crash only triggers with
execution.)

gdb/ChangeLog:
2017-03-07  Pedro Alves  <[email protected]>

	* tui/tui-regs.c (tui_restore_gdbout): Don't delete gdb_stdout.

gdb/testsuite/ChangeLog:
2017-03-07  Pedro Alves  <[email protected]>

	* gdb.base/tui-layout.c: New file.
	* gdb.base/tui-layout.exp: New file.

Author: palves

gdb/ChangeLog

@@ -1,3 +1,7 @@
+2017-03-07  Pedro Alves  <[email protected]>
+
+	* tui/tui-regs.c (tui_restore_gdbout): Don't delete gdb_stdout.
+
 2017-03-07  Walfred Tedeschi  <[email protected]>
 
 	* i387-tdep.h (i387_reset_bnd_regs): Add function definition.

gdb/testsuite/ChangeLog

@@ -1,3 +1,8 @@
+2017-03-07  Pedro Alves  <[email protected]>
+
+	* gdb.base/tui-layout.c: New file.
+	* gdb.base/tui-layout.exp: New file.
+
 2017-03-07  Pedro Alves  <[email protected]>
 
 	* gdb.base/tui-layout.c: Rename to ...

gdb/testsuite/gdb.base/tui-layout.c

@@ -0,0 +1,22 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2017 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+int
+main ()
+{
+  return 0;
+}

gdb/testsuite/gdb.base/tui-layout.exp

@@ -0,0 +1,56 @@
+# Copyright 2017 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# Minimal testcase that just checks that the various "layout $foo"
+# commands do not cause gdb to crash.
+
+standard_testfile
+
+if {[prepare_for_testing "failed to prepare" ${testfile} ${srcfile}]} {
+    return -1
+}
+
+if {[skip_tui_tests]} {
+    return
+}
+
+# Test one layout command.  EXECUTION indicates whether to activate
+# the layout with or without execution.
+
+proc test_layout {layout execution} {
+    global binfile gdb_prompt
+
+    clean_restart $binfile
+
+    if {$execution} {
+	if ![runto_main] then {
+	    fail "can't run to main"
+	    return 0
+	}
+    }
+
+    set test "layout command"
+    gdb_test_multiple "layout $layout" $test {
+	-re "$gdb_prompt $" {
+	    pass $test
+	}
+    }
+}
+
+foreach_with_prefix execution {0 1} {
+    foreach_with_prefix layout {"asm" "reg" "src" "split"} {
+	test_layout $layout $execution
+    }
+}

gdb/tui/tui-regs.c

@@ -711,7 +711,6 @@ TUI command to control the register window."), tuicmd);
 static void
 tui_restore_gdbout (void *ui)
 {
-  delete gdb_stdout;
   gdb_stdout = (struct ui_file*) ui;
   pagination_enabled = 1;
 }