gdb/mi: preserve user selected thread and frame when invoking MI commands

Fix for PR gdb/20684.  When invoking MI commands with --thread and/or
--frame, the user selected thread and frame was not preserved:

  (gdb)
  info thread
  &"info thread\n"
  ~"  Id   Target Id                                           Frame \n"
  ~"* 1    Thread 0x7ffff7c30740 (LWP 19302) \"user-selected-c\" main () at /home/uuu/gdb/gdb/testsuite/gdb.mi/user-selected-context-sync.c:60\n"
  ~"  2    Thread 0x7ffff7c2f700 (LWP 19306) \"user-selected-c\" child_sub_function () at /home/uuu/gdb/gdb/testsuite/gdb.mi/user-selected-context-sync.c:30\n"
  ~"  3    Thread 0x7ffff742e700 (LWP 19307) \"user-selected-c\" child_sub_function () at /home/uuu/gdb/gdb/testsuite/gdb.mi/user-selected-context-sync.c:30\n"
  ^done
  (gdb)
  info frame
  &"info frame\n"
  ~"Stack level 0, frame at 0x7fffffffdf90:\n"
  ~" rip = 0x555555555207 in main (/home/uuu/gdb/gdb/testsuite/gdb.mi/user-selected-context-sync.c:60); saved rip = 0x7ffff7c5709b\n"
  ~" source language c.\n"
  ~" Arglist at 0x7fffffffdf80, args: \n"
  ~" Locals at 0x7fffffffdf80, Previous frame's sp is 0x7fffffffdf90\n"
  ~" Saved registers:\n "
  ~" rbp at 0x7fffffffdf80, rip at 0x7fffffffdf88\n"
  ^done
  (gdb)
  -stack-info-depth --thread 3
  ^done,depth="4"
  (gdb)
  info thread
  &"info thread\n"
  ~"  Id   Target Id                                           Frame \n"
  ~"  1    Thread 0x7ffff7c30740 (LWP 19302) \"user-selected-c\" main () at /home/uuu/gdb/gdb/testsuite/gdb.mi/user-selected-context-sync.c:60\n"
  ~"  2    Thread 0x7ffff7c2f700 (LWP 19306) \"user-selected-c\" child_sub_function () at /home/uuu/gdb/gdb/testsuite/gdb.mi/user-selected-context-sync.c:30\n"
  ~"* 3    Thread 0x7ffff742e700 (LWP 19307) \"user-selected-c\" child_sub_function () at /home/uuu/gdb/gdb/testsuite/gdb.mi/user-selected-context-sync.c:30\n"
  ^done
  (gdb)
  info frame
  &"info frame\n"
  ~"Stack level 0, frame at 0x7ffff742dee0:\n"
  ~" rip = 0x555555555169 in child_sub_function (/home/uuu/gdb/gdb/testsuite/gdb.mi/user-selected-context-sync.c:30); saved rip = 0x555555555188\n"
  ~" called by frame at 0x7ffff742df00\n"
  ~" source language c.\n"
  ~" Arglist at 0x7ffff742ded0, args: \n"
  ~" Locals at 0x7ffff742ded0, Previous frame's sp is 0x7ffff742dee0\n"
  ~" Saved registers:\n "
  ~" rbp at 0x7ffff742ded0, rip at 0x7ffff742ded8\n"
  ^done
  (gdb)

This caused problems for frontends that provide access to CLI because UI
may silently change the context for CLI commands (as demonstrated above).

This commit fixes the problem by restoring thread and frame in
mi_cmd_execute (). With this change, there are only two GDB/MI commands
that can change user selected context: -thread-select and -stack-select-frame.
This allows us to remove all and rather complicated logic of notifying
about user selected context change from mi_execute_command (), leaving it
to these two commands themselves to notify.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=20684

1 files changed, 157 insertions, 0 deletions

diff --git a/gdb/testsuite/gdb.mi/mi-cmd-user-context.exp b/gdb/testsuite/gdb.mi/mi-cmd-user-context.exp
new file mode 100644
index 0000000..d7417d5
--- /dev/null
+++ b/gdb/testsuite/gdb.mi/mi-cmd-user-context.exp
@@ -0,0 +1,157 @@
+# Copyright 2022 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/>.
+
+# Test that GDB/MI commands preserve user selected context when
+# passed --thread and/or --frame.
+
+load_lib mi-support.exp
+
+standard_testfile user-selected-context-sync.c
+
+if {[build_executable $testfile.exp $testfile ${srcfile} "debug pthreads"] == -1} {
+    untested "failed to compile"
+    return -1
+}
+
+set main_break_line [gdb_get_line_number "main break line"]
+
+set any "\[^\r\n\]*"
+
+mi_clean_restart $binfile
+mi_create_breakpoint "$srcfile:$main_break_line" "set breakpoint in main"
+mi_run_cmd
+mi_expect_stop "breakpoint-hit" "main" "" $srcfile $main_break_line \
+	 { "" "disp=\"keep\"" } "run to breakpoint in main"
+
+mi_gdb_test "thread" \
+	".*Current thread is 1.*" \
+	"info thread 1"
+
+# Run -stack-info-depth in a different thread, the current thread
+# should not change.
+
+mi_gdb_test "-stack-info-depth --thread 3" \
+    "\\^done,depth=.*" \
+    "-stack-info-depth --thread 3"
+
+mi_gdb_test "thread" \
+    ".*Current thread is 1.*" \
+    "info thread 2"
+
+# Expect GDB to switch to thread 3.
+mi_gdb_test "-thread-select 3" \
+    "\\^done,${any}new-thread-id=\"3\"${any}" \
+    "-thread-select 3"
+
+mi_gdb_test "thread" \
+    ".*Current thread is 3.*" \
+    "info thread 3"
+
+# Expect GDB to switch to thread 1.
+mi_gdb_test "-thread-select --thread 2 1" \
+    "\\^done,${any}new-thread-id=\"1\"${any}" \
+    "-thread-select --thread 2 1"
+
+mi_gdb_test "thread" \
+    ".*Current thread is 1.*" \
+    "info thread 4"
+
+# Expect GDB to switch to thread 2.
+mi_gdb_test "-thread-select --thread 2 2" \
+    "\\^done,.*" \
+    "-thread-select --thread 2 2"
+
+mi_gdb_test "thread" \
+    ".*Current thread is 2.*" \
+    "info thread 5"
+
+# Check we're in frame 0.
+mi_gdb_test "frame" \
+    ".*#0  0x.*" \
+    "frame 1"
+
+# Ask about a different frame in the current thread, the current frame
+# should not change.
+mi_gdb_test "-stack-info-frame --thread 2 --frame 1" \
+    "\\^done,frame=\{level=\"1\".*" \
+    "-stack-info-frame 1"
+
+mi_gdb_test "thread" \
+    ".*Current thread is 2.*" \
+    "info thread 6"
+
+mi_gdb_test "frame" \
+    ".*#0  0x.*" \
+    "frame 2"
+
+
+# Ask about a different frame in a different thread.  After this the
+# current thread and frame should not have changed.
+mi_gdb_test "-stack-info-frame --thread 3 --frame 1" \
+    "\\^done,frame=\{level=\"1\".*" \
+    "-stack-info-frame 2"
+
+mi_gdb_test "thread" \
+    ".*Current thread is 2.*" \
+    "info thread 7"
+
+mi_gdb_test "frame" \
+    ".*#0  0x.*" \
+    "frame 3"
+
+# Select a different frame in the current thread.  Despite the use of
+# the --frame option, we do expect the currently selected frame to
+# change.
+mi_gdb_test "-stack-select-frame --thread 2 --frame 0 1" \
+    "\\^done" \
+    "--stack-select-frame 1"
+
+mi_gdb_test "thread" \
+    ".*Current thread is 2.*" \
+    "info thread 8"
+
+mi_gdb_test "frame" \
+    ".*#1  0x.*" \
+    "frame 4"
+
+# Similar to the previous test, but this time the --frame option is
+# the same as the frame we are selecting.  We still expect GDB to
+# update the currently selected frame.
+mi_gdb_test "-stack-select-frame --thread 2 --frame 2 2" \
+    "\\^done" \
+    "--stack-select-frame 2"
+
+mi_gdb_test "thread" \
+    ".*Current thread is 2.*" \
+    "info thread 9"
+
+mi_gdb_test "frame" \
+    ".*#2  0x.*" \
+    "frame 5"
+
+# Now select a frame in a different thread.  We expect both the
+# currently selected thread, and the currently selected frame to be
+# updated.
+mi_gdb_test "-stack-select-frame --thread 1 --frame 0 0" \
+    "\\^done" \
+    "--stack-select-frame 3"
+
+mi_gdb_test "thread" \
+    ".*Current thread is 1.*" \
+    "info thread 10"
+
+mi_gdb_test "frame" \
+    ".*#0  main.*" \
+    "frame 6"