Re: [PATCH v3 7/7] Add $_gthread convenience variable

Simon Marchi
2016-01-06T19:14:07Z

On 16-01-06 08:03 AM, Pedro Alves wrote:
> This commit adds a new $_gthread convenience variable, that is like
> $_thread, but holds the current thread's global thread id.
>
> gdb/ChangeLog:
> 2016-01-06 Pedro Alves <palves@redhat.com>
>
> * NEWS: Mention $_gthread.
> * gdbthread.h (struct thread_info) <global_num>: Mention
> $_gthread.
> * thread.c (thread_num_make_value_helper): New function.
> (thread_id_make_value): Delete.
> (thread_id_per_inf_num_make_value, global_thread_id_make_value):
> New.
> (thread_funcs): Adjust.
> (gthread_funcs): New.
> (_initialize_thread): Register $_gthread variable.
>
> gdb/testsuite/ChangeLog:
> 2016-01-06 Pedro Alves <palves@redhat.com>
>
> * gdb.base/default.exp: Expect $_gthread as well.
> * gdb.multi/tids.exp: Test $_gthread.
> * gdb.threads/thread-specific.exp: Test $_gthread.
>
> gdb/doc/ChangeLog:
> 2016-01-06 Pedro Alves <palves@redhat.com>
>
> * gdb.texinfo (Threads): Document the $_gthread convenience
> variable.
> (Convenience Vars): Likewise.
> ---
> gdb/NEWS | 5 ++-
> gdb/doc/gdb.texinfo | 9 +++--
> gdb/gdbthread.h | 3 +-
> gdb/testsuite/gdb.base/default.exp | 1 +
> gdb/testsuite/gdb.multi/tids.exp | 3 +-
> gdb/testsuite/gdb.threads/thread-specific.exp | 5 +++
> gdb/thread.c | 49 +++++++++++++++++++++++----
> 7 files changed, 64 insertions(+), 11 deletions(-)
>
> diff --git a/gdb/NEWS b/gdb/NEWS
> index 32e7bd3..e4791cd 100644
> --- a/gdb/NEWS
> +++ b/gdb/NEWS
> @@ -22,7 +22,7 @@
>
> GDB now maintains a second thread ID per thread, referred to as the
> global thread ID, which is the new equivalent of thread numbers in
> - previous releases.
> + previous releases. See also $_gthread below.
>
> For backwards compatibility, MI's thread IDs always refer to global
> IDs.
> @@ -37,6 +37,9 @@
> * You can use "info threads -gid" to display the global thread ID of
> all threads.
>
> +* The new convenience variable $_gthread holds the global number of
> + the current thread.
> +
> * The new convenience variable $_inferior holds the number of the
> current inferior.
>
> diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
> index 8ce3b01..f1e5aab 100644
> --- a/gdb/doc/gdb.texinfo
> +++ b/gdb/doc/gdb.texinfo
> @@ -2937,8 +2937,10 @@ thread. In other words, @value{GDBN} assigns a thread number to the
> program's ``main thread'' even if the program is not multi-threaded.
>
> @vindex $_thread@r{, convenience variable}
> -The debugger convenience variable @samp{$_thread} contains the
> -per-inferior thread number of the current thread. You may find this
> +@vindex $_gthread@r{, convenience variable}
> +The debugger convenience variables @samp{$_thread} and
> +@samp{$_gthread} contain, respectively, the per-inferior thread number
> +and the global thread number of the current thread. You may find this
> useful in writing breakpoint conditional expressions, command scripts,
> and so forth. @xref{Convenience Vars,, Convenience Variables}, for
> general information on convenience variables.
> @@ -10459,6 +10461,9 @@ Programs, ,Debugging Multiple Inferiors and Programs}.
> @item $_thread
> The thread number of the current thread. @xref{thread numbers}.
>
> +@item $_gthread
> +The global number of the current thread. @xref{global thread numbers}.
> +
> @end table
>
> @node Convenience Funs
> diff --git a/gdb/gdbthread.h b/gdb/gdbthread.h
> index b8d5ac2..f021c65 100644
> --- a/gdb/gdbthread.h
> +++ b/gdb/gdbthread.h
> @@ -217,7 +217,8 @@ struct thread_info
> thread has its own unique global ID. */
>
> /* The thread's global GDB thread number. This is exposed to MI,
> - Python/Scheme and visible with "info threads -gid". */
> + Python/Scheme, visible with "info threads -gid", and is also what
> + the $_gthread convenience variable is bound to. */
> int global_num;
>
> /* The per-inferior thread number. This is unique in the inferior
> diff --git a/gdb/testsuite/gdb.base/default.exp b/gdb/testsuite/gdb.base/default.exp
> index fec2cde..10739ca 100644
> --- a/gdb/testsuite/gdb.base/default.exp
> +++ b/gdb/testsuite/gdb.base/default.exp
> @@ -587,6 +587,7 @@ set show_conv_list \
> {$_sdata = void} \
> {$_siginfo = void} \
> {$_thread = 0} \
> + {$_gthread = 0} \
> {$_inferior = 1} \
> {$_exception = <error: No frame selected>} \
> {$_probe_argc = <error: No frame selected>} \
> diff --git a/gdb/testsuite/gdb.multi/tids.exp b/gdb/testsuite/gdb.multi/tids.exp
> index badb1f1..cc5f487 100644
> --- a/gdb/testsuite/gdb.multi/tids.exp
> +++ b/gdb/testsuite/gdb.multi/tids.exp
> @@ -158,8 +158,9 @@ with_test_prefix "two inferiors" {
> " 2\.1 +2 +.*" \
> " 2\.2 +3 +.* thread_function1 .* at .*$srcfile:.*"]
>
> - # Confirm the convenience variable show the expected number.
> + # Confirm the convenience variables show the expected numbers.
> gdb_test "p \$_thread == 2" " = 1"
> + gdb_test "p \$_gthread == 4" " = 1"
>
> # Without an explicit inferior component, GDB defaults to the
> # current inferior. Make sure we don't refer to a thread by
> diff --git a/gdb/testsuite/gdb.threads/thread-specific.exp b/gdb/testsuite/gdb.threads/thread-specific.exp
> index 2b75b60..8f61f88 100644
> --- a/gdb/testsuite/gdb.threads/thread-specific.exp
> +++ b/gdb/testsuite/gdb.threads/thread-specific.exp
> @@ -66,7 +66,10 @@ clean_restart ${binfile}
> gdb_test_no_output "set print sevenbit-strings"
> gdb_test_no_output "set width 0"
>
> +# As this test only runs a single inferior, $_thread and $_gthread
> +# should match throughout.
> gdb_test {print $_thread} ".* = 0" "thread var when not running"
> +gdb_test {print $_gthread} ".* = 0" "gthread var when not running"
>
> runto_main
>
> @@ -82,6 +85,7 @@ if {[llength $threads] == 0} {
> }
>
> gdb_test {print $_thread} ".* = [lindex $threads 0]" "thread var in main"
> +gdb_test {print $_gthread} ".* = [lindex $threads 0]" "gthread var in main"
>
> gdb_test_multiple "break $line thread [lindex $threads 0]" \
> "breakpoint $line main thread" {
> @@ -120,6 +124,7 @@ if { $this_breakpoint != -1 } {
>
> if { $this_thread != -1 } {
> gdb_test {print $_thread} ".* = $this_thread" "thread var at break"
> + gdb_test {print $_gthread} ".* = $this_thread" "gthread var at break"
> } else {
> untested "thread var at break"
> }
> diff --git a/gdb/thread.c b/gdb/thread.c
> index 24eb83e..43441ee 100644
> --- a/gdb/thread.c
> +++ b/gdb/thread.c
> @@ -2061,18 +2061,45 @@ update_thread_list (void)
> update_threads_executing ();
> }
>
> +/* Return a new value for the selected thread's id. Return a value of
> + 0 if no thread is selected. If GLOBAL is true, return the thread's
> + global number. Otherwise return the per-inferior number. */
> +
> +static struct value *
> +thread_num_make_value_helper (struct gdbarch *gdbarch, int global)
> +{
> + struct thread_info *tp = find_thread_ptid (inferior_ptid);
> + int int_val;
> +
> + if (tp == NULL)
> + int_val = 0;
> + else if (global)
> + int_val = tp->global_num;
> + else
> + int_val = tp->per_inf_num;
> +
> + return value_from_longest (builtin_type (gdbarch)->builtin_int, int_val);
> +}
> +
> /* Return a new value for the selected thread's per-inferior thread
> number. Return a value of 0 if no thread is selected, or no
> threads exist. */
>
> static struct value *
> -thread_id_make_value (struct gdbarch *gdbarch, struct internalvar *var,
> - void *ignore)
> +thread_id_per_inf_num_make_value (struct gdbarch *gdbarch, struct internalvar *var,
> + void *ignore)
> {
> - struct thread_info *tp = find_thread_ptid (inferior_ptid);
> + return thread_num_make_value_helper (gdbarch, 0);
> +}
> +
> +/* Return a new value for the selected thread's global id. Return a
> + value of 0 if no thread is selected, or no threads exist. */
>
> - return value_from_longest (builtin_type (gdbarch)->builtin_int,
> - (tp ? tp->per_inf_num : 0));
> +static struct value *
> +global_thread_id_make_value (struct gdbarch *gdbarch, struct internalvar *var,
> + void *ignore)
> +{
> + return thread_num_make_value_helper (gdbarch, 1);
> }
>
> /* Commands with a prefix of `thread'. */
> @@ -2082,7 +2109,16 @@ struct cmd_list_element *thread_cmd_list = NULL;
>
> static const struct internalvar_funcs thread_funcs =
> {
> - thread_id_make_value,
> + thread_id_per_inf_num_make_value,
> + NULL,
> + NULL
> +};
> +
> +/* Implementation of `gthread' variable. */
> +
> +static const struct internalvar_funcs gthread_funcs =
> +{
> + global_thread_id_make_value,
> NULL,
> NULL
> };
> @@ -2140,6 +2176,7 @@ Show printing of thread events (such as thread start and exit)."), NULL,
> &setprintlist, &showprintlist);
>
> create_internalvar_type_lazy ("_thread", &thread_funcs, NULL);
> + create_internalvar_type_lazy ("_gthread", &gthread_funcs, NULL);
>
> observer_attach_thread_ptid_changed (restore_current_thread_ptid_changed);
> }
>

LGTM.