gdb: print thread names in thread apply command output

  This makes the thread apply command print the thread's name.  The use
of target_pid_to_str is replaced by thread_target_id_str, which
provides the same output as "info threads".

Before:
(gdb) thread apply 2 bt

Thread 2 (Thread 0x7fd245602700 (LWP 3837)):
[...]

After:
(gdb) thread apply 2 bt

Thread 2 (Thread 0x7fd245602700 (LWP 3837) "HT cleanup"):
[...]

The thread's description header is pre-computed before running the
command since the command may change the selected inferior. This is
not permitted by thread_target_id_str as target_thread_name asserts
that `info->inf == current_inferior ()`.

This situation arises in the `gdb.threads/threadapply.exp` test which
kills and removes the inferior as part of a "thread apply" command.

gdb/ChangeLog:

        * thread.c (thr_try_catch_cmd): Print thread name.
---
 gdb/ChangeLog |  4 ++++
 gdb/thread.c  | 16 ++++++++++------
 2 files changed, 14 insertions(+), 6 deletions(-)
  

Hi,

Thanks for the patch. Some comments below.

On 2/17/20 7:30 PM, Jérémie Galarneau wrote:
> This makes the thread apply command print the thread's name.  The use
> of target_pid_to_str is replaced by thread_target_id_str, which
> provides the same output as "info threads".

Is this a cosmetic change to the way GDB outputs things? If so, I wonder 
if the current tests expect the old format and thus will start to fail 
with the new output? Have you exercised the testsuite?

> 
> Before:
> (gdb) thread apply 2 bt
> 
> Thread 2 (Thread 0x7fd245602700 (LWP 3837)):
> [...]
> 
> After:
> (gdb) thread apply 2 bt
> 
> Thread 2 (Thread 0x7fd245602700 (LWP 3837) "HT cleanup"):
> [...]
> 
> The thread's description header is pre-computed before running the
> command since the command may change the selected inferior. This is
> not permitted by thread_target_id_str as target_thread_name asserts
> that `info->inf == current_inferior ()`.
> 
> This situation arises in the `gdb.threads/threadapply.exp` test which
> kills and removes the inferior as part of a "thread apply" command.
> 
> gdb/ChangeLog:
> 
>          * thread.c (thr_try_catch_cmd): Print thread name.
> ---
>   gdb/ChangeLog |  4 ++++
>   gdb/thread.c  | 16 ++++++++++------
>   2 files changed, 14 insertions(+), 6 deletions(-)
> 
> diff --git a/gdb/ChangeLog b/gdb/ChangeLog
> index dafd90ec37..4fce196187 100644
> --- a/gdb/ChangeLog
> +++ b/gdb/ChangeLog
> @@ -1,3 +1,7 @@
> +2020-02-17  Jérémie Galarneau  <jeremie.galarneau@efficios.com>
> +
> +	* thread.c (thr_try_catch_cmd): Print thread name.
> +
>   2020-02-14  Simon Marchi  <simon.marchi@efficios.com>
>   
>   	* aarch64-tdep.c (aarch64_displaced_step_copy_insn): Use
> diff --git a/gdb/thread.c b/gdb/thread.c
> index 54b59e2244..0c1611bdc1 100644
> --- a/gdb/thread.c
> +++ b/gdb/thread.c
> @@ -1563,6 +1563,14 @@ thr_try_catch_cmd (thread_info *thr, const char *cmd, int from_tty,
>   		   const qcs_flags &flags)
>   {
>     switch_to_thread (thr);
> +
> +  /* The thread header is computed before running the command since
> +   * the command can change the inferior, which is not permitted
> +   * by thread_target_id_str.  */

The formatting of the comment block is not right. We don't start 
intermediate lines with *. You can check existing blocks for the format 
that we use.

> +  std::string thr_header = string_printf(_("\nThread %s (%s):\n"),
> +					 print_thread_id (thr),
> +					 thread_target_id_str (thr).c_str ());

Maybe write it as:

std::string thr_header =
   string_printf(_("\nThread %s (%s):\n"), print_thread_id (thr),
                 thread_target_id_str (thr).c_str ());

I think it gives it a better alignment. Just a suggestion.

> +
>     try
>       {
>         std::string cmd_result = execute_command_to_string
> @@ -1570,9 +1578,7 @@ thr_try_catch_cmd (thread_info *thr, const char *cmd, int from_tty,
>         if (!flags.silent || cmd_result.length () > 0)
>   	{
>   	  if (!flags.quiet)
> -	    printf_filtered (_("\nThread %s (%s):\n"),
> -			     print_thread_id (thr),
> -			     target_pid_to_str (inferior_ptid).c_str ());
> +	    printf_filtered ("%s", thr_header.c_str ());
>   	  printf_filtered ("%s", cmd_result.c_str ());
>   	}
>       }
> @@ -1581,9 +1587,7 @@ thr_try_catch_cmd (thread_info *thr, const char *cmd, int from_tty,
>         if (!flags.silent)
>   	{
>   	  if (!flags.quiet)
> -	    printf_filtered (_("\nThread %s (%s):\n"),
> -			     print_thread_id (thr),
> -			     target_pid_to_str (inferior_ptid).c_str ());
> +	    printf_filtered ("%s", thr_header.c_str ());
>   	  if (flags.cont)
>   	    printf_filtered ("%s\n", ex.what ());
>   	  else
>
  

On Mon, 17 Feb 2020 at 18:17, Luis Machado <luis.machado@linaro.org> wrote:
>
> Hi,
>
> Thanks for the patch. Some comments below.
>
> On 2/17/20 7:30 PM, Jérémie Galarneau wrote:
> > This makes the thread apply command print the thread's name.  The use
> > of target_pid_to_str is replaced by thread_target_id_str, which
> > provides the same output as "info threads".
>
> Is this a cosmetic change to the way GDB outputs things? If so, I wonder
> if the current tests expect the old format and thus will start to fail
> with the new output? Have you exercised the testsuite?

Hi,

It does indeed introduce a cosmetic change. I have exercised the test
suite with and without my patch applied. The only difference I see is
"gdb.threads/process-dies-while-handling-bp.exp" which sometimes
passes/fails, but I think this test is known to be flaky.

>
> >
> > Before:
> > (gdb) thread apply 2 bt
> >
> > Thread 2 (Thread 0x7fd245602700 (LWP 3837)):
> > [...]
> >
> > After:
> > (gdb) thread apply 2 bt
> >
> > Thread 2 (Thread 0x7fd245602700 (LWP 3837) "HT cleanup"):
> > [...]
> >
> > The thread's description header is pre-computed before running the
> > command since the command may change the selected inferior. This is
> > not permitted by thread_target_id_str as target_thread_name asserts
> > that `info->inf == current_inferior ()`.
> >
> > This situation arises in the `gdb.threads/threadapply.exp` test which
> > kills and removes the inferior as part of a "thread apply" command.
> >
> > gdb/ChangeLog:
> >
> >          * thread.c (thr_try_catch_cmd): Print thread name.
> > ---
> >   gdb/ChangeLog |  4 ++++
> >   gdb/thread.c  | 16 ++++++++++------
> >   2 files changed, 14 insertions(+), 6 deletions(-)
> >
> > diff --git a/gdb/ChangeLog b/gdb/ChangeLog
> > index dafd90ec37..4fce196187 100644
> > --- a/gdb/ChangeLog
> > +++ b/gdb/ChangeLog
> > @@ -1,3 +1,7 @@
> > +2020-02-17  Jérémie Galarneau  <jeremie.galarneau@efficios.com>
> > +
> > +     * thread.c (thr_try_catch_cmd): Print thread name.
> > +
> >   2020-02-14  Simon Marchi  <simon.marchi@efficios.com>
> >
> >       * aarch64-tdep.c (aarch64_displaced_step_copy_insn): Use
> > diff --git a/gdb/thread.c b/gdb/thread.c
> > index 54b59e2244..0c1611bdc1 100644
> > --- a/gdb/thread.c
> > +++ b/gdb/thread.c
> > @@ -1563,6 +1563,14 @@ thr_try_catch_cmd (thread_info *thr, const char *cmd, int from_tty,
> >                  const qcs_flags &flags)
> >   {
> >     switch_to_thread (thr);
> > +
> > +  /* The thread header is computed before running the command since
> > +   * the command can change the inferior, which is not permitted
> > +   * by thread_target_id_str.  */
>
> The formatting of the comment block is not right. We don't start
> intermediate lines with *. You can check existing blocks for the format
> that we use.

Right! Sorry about that.

>
> > +  std::string thr_header = string_printf(_("\nThread %s (%s):\n"),
> > +                                      print_thread_id (thr),
> > +                                      thread_target_id_str (thr).c_str ());
>
> Maybe write it as:
>
> std::string thr_header =
>    string_printf(_("\nThread %s (%s):\n"), print_thread_id (thr),
>                  thread_target_id_str (thr).c_str ());
>
> I think it gives it a better alignment. Just a suggestion.

Alright, I'll send a v2 with those comments addressed.

Thanks for the review!
Jérémie

>
> > +
> >     try
> >       {
> >         std::string cmd_result = execute_command_to_string
> > @@ -1570,9 +1578,7 @@ thr_try_catch_cmd (thread_info *thr, const char *cmd, int from_tty,
> >         if (!flags.silent || cmd_result.length () > 0)
> >       {
> >         if (!flags.quiet)
> > -         printf_filtered (_("\nThread %s (%s):\n"),
> > -                          print_thread_id (thr),
> > -                          target_pid_to_str (inferior_ptid).c_str ());
> > +         printf_filtered ("%s", thr_header.c_str ());
> >         printf_filtered ("%s", cmd_result.c_str ());
> >       }
> >       }
> > @@ -1581,9 +1587,7 @@ thr_try_catch_cmd (thread_info *thr, const char *cmd, int from_tty,
> >         if (!flags.silent)
> >       {
> >         if (!flags.quiet)
> > -         printf_filtered (_("\nThread %s (%s):\n"),
> > -                          print_thread_id (thr),
> > -                          target_pid_to_str (inferior_ptid).c_str ());
> > +         printf_filtered ("%s", thr_header.c_str ());
> >         if (flags.cont)
> >           printf_filtered ("%s\n", ex.what ());
> >         else
> >
  

On 2020-02-17 7:01 p.m., Jérémie Galarneau wrote:
>>> +  std::string thr_header = string_printf(_("\nThread %s (%s):\n"),
>>> +                                      print_thread_id (thr),
>>> +                                      thread_target_id_str (thr).c_str ());
>>
>> Maybe write it as:
>>
>> std::string thr_header =
>>    string_printf(_("\nThread %s (%s):\n"), print_thread_id (thr),
>>                  thread_target_id_str (thr).c_str ());
>>
>> I think it gives it a better alignment. Just a suggestion.
> 
> Alright, I'll send a v2 with those comments addressed.

Actually, the GNU styles breaks lines before binary operators, including
the assignment operator.  See this for example:

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;a=blob;f=gdb/thread.c;h=54b59e22448a260e4190ffe5438b8b5c799a1cd9;hb=HEAD#l1888

No need to send another version just for that, we can fix it up when we
push the patch.

Simon