[pushed] gdb/mi: consistently notify user when GDB/MI client uses -thread-select

[Jan Vrany]

Hi,

On Wed, 2022-03-23 at 08:36 -0400, Simon Marchi wrote:
> > Just tried on Ubuntu 20.04 and I do not any problem. 
> 
> I'm trying to look a bit more into it.  The state is that we have thread
> 2 already selected, issue a `-thread-select 2` on the MI UI, and expect
> to not have a CLI notification to say that the thread changed, since we
> try to select the already selected thread.
> 
> Before your patch I get:
> 
>     -thread-select 2
> 
>     ^done,new-thread-id="2",frame={level="0",addr="0x00005555555551b8",func="child_sub_function",args=[],file="/home/smarchi/src/binutils-
> gdb/gdb/testsuite/gdb.mi/user-selected-context-sync.c",fullname="/home/smarchi/src/binutils-gdb/gdb/testsuite/gdb.mi/user-selected-context-
> sync.c",line="33",arch="i386:x86-64"}
> 
>     (gdb) 
> 
>     PASS: gdb.mi/user-selected-context-sync.exp: mode=all-stop: test_mi_thread_select: thread 1.2: -thread-select again
>     print 666
> 
>     $9 = 666
> 
>     (gdb) PASS: gdb.mi/user-selected-context-sync.exp: mode=all-stop: test_mi_thread_select: thread 1.2: -thread-select again, event on CLI, ensure no output
> CLI
> 
> After:
> 
>     -thread-select 2
> 
>     ^done,new-thread-id="2",frame={level="0",addr="0x00005555555551b8",func="child_sub_function",args=[],file="/home/smarchi/src/binutils-
> gdb/gdb/testsuite/gdb.mi/user-selected-context-sync.c",fullname="/home/smarchi/src/binutils-gdb/gdb/testsuite/gdb.mi/user-selected-context-
> sync.c",line="33",arch="i386:x86-64"}
> 
>     (gdb) 
> 
>     PASS: gdb.mi/user-selected-context-sync.exp: mode=all-stop: test_mi_thread_select: thread 1.2: -thread-select again
>     [Switching to thread 1.2 (Thread 0x7ffff7d99700 (LWP 1885257))]
> 
>     #0  child_sub_function () at /home/smarchi/src/binutils-gdb/gdb/testsuite/gdb.mi/user-selected-context-sync.c:33
> 
>     33	    dummy = !dummy; /* thread loop line */
> 
>     print 666
> 
>     $9 = 666
> 
>     (gdb) FAIL: gdb.mi/user-selected-context-sync.exp: mode=all-stop: test_mi_thread_select: thread 1.2: -thread-select again, event on CLI, ensure no output
> CLI
> 
> So there is really a spurious "Switching to thread 1.2" notification in
> my case.
> 
> Trying a simpler case, just an empty main program, I do this (/dev/pts/8
> being the tty for my MI UI):
> 
>     $ ./gdb -q -nx --data-directory=data-directory a.out -ex "new-ui mi /dev/pts/8" -ex start
> 
> If I then type `-thread-select 1` on the MI UI, I do get:
> 
>     [Switching to thread 1 (process 1891548)]
> 
> ... which is unexpected.  Before your patch, I don't get it.  Can you
> give this small test a try?
> 

I gave it a go but I'm sorry: everything seem to work as expected 
here. I do not get "[Switching to thread 1 (process 1891548)]" message
on CLI when -thread-select already selected thread. 

I must be doing something differently. What commit is failing for you?
What's your ./configure incantation?

I'm happy to sit down with you and have a closer look at this, maybe using 
IRC or something. 

Jan




> Simon