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

Pedro Alves
2016-01-06T13:11:06Z

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);
}
--
1.9.3