GDB notifies users about user selected thread changes somewhat
inconsistently as mentioned on gdb-patches mailing list here:
https://sourceware.org/pipermail/gdb-patches/2022-February/185989.html
Consider GDB debugging a multi-threaded inferior with both CLI and GDB/MI
interfaces connected to separate terminals.
Assuming inferior is stopped and thread 1 is selected, when a thread
2 is selected using '-thread-select 2' command on GDB/MI terminal:
-thread-select 2
^done,new-thread-id="2",frame={level="0",addr="0x00005555555551cd",func="child_sub_function",args=[],file="/home/jv/Projects/gdb/users_jv_patches/gdb/testsuite/gdb.mi/user-selected-context-sync.c",fullname="/home/uuu/gdb/gdb/testsuite/gdb.mi/user-selected-context-sync.c",line="30",arch="i386:x86-64"}
(gdb)
and on CLI terminal we get the notification (as expected):
[Switching to thread 2 (Thread 0x7ffff7daa640 (LWP 389659))]
#0 child_sub_function () at /home/uuu/gdb/gdb/testsuite/gdb.mi/user-selected-context-sync.c:30
30 volatile int dummy = 0;
However, now that thread 2 is selected, if thread 1 is selected
using 'thread-select --thread 1 1' command on GDB/MI terminal
terminal:
-thread-select --thread 1 1
^done,new-thread-id="1",frame={level="0",addr="0x0000555555555294",func="main",args=[],file="/home/jv/Projects/gdb/users_jv_patches/gdb/testsuite/gdb.mi/user-selected-context-sync.c",fullname="/home/jv/Projects/gdb/users_jv_patches/gdb/testsuite/gdb.mi/user-selected-context-sync.c",line="66",arch="i386:x86-64"}
(gdb)
but no notification is printed on CLI terminal, despite the fact
that user selected thread has changed.
The problem is that when `-thread-select --thread 1 1` is executed
then thread is switched to thread 1 before mi_cmd_thread_select () is
called, therefore the condition "inferior_ptid != previous_ptid"
there does not hold.
To address this problem, we have to move notification logic up to
mi_cmd_execute () where --thread option is processed and notify
user selected contents observers there if context changes.
However, this in itself breaks GDB/MI because it would cause context
notification to be sent on MI channel. This is because by the time
we notify, MI notification suppression is already restored (done in
mi_command::invoke(). Therefore we had to lift notification suppression
logic also up to mi_cmd_execute (). This change in made distinction
between mi_command::invoke() and mi_command::do_invoke() unnecessary
as all mi_command::invoke() did (after the change) was to call
do_invoke(). So this patches removes do_invoke() and moves the command
execution logic directly to invoke().
With this change, all gdb.mi tests pass, tested on x86_64-linux.
Co-authored-by: Andrew Burgess <aburgess@redhat.com>
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=20631
a2757c4ed6