[PATCH 4/4] Test case for gdb.thread_from_thread_handle

[Kevin Buettner <kevinb@redhat.com>]

As the title says, this is a test case for
gdb.thread_from_thread_handle, a python function which will, given a
thread library dependent thread handle, find the GDB thread which
corresponds to that thread handle.

The C file for this test case causes the thread handles for the
main thread and two child threads to be placed into an array.  The
test case runs to one of the functions (do_something()) at which point,
it retrieves the thread handles from the array and attempts to find the
correponding thread in GDB's internal thread list.

I use a barrier to make sure that both threads have actually started;
execution will stop when one of the threads breaks at do_something.

The one concern I have about what I've written is with the last three
invocations of gdb_test.  I don't know that we can be certain that
thrs[1] will always map to GDB thread 2 and that thrs[2] will map to
GDB thread 3.  It seems likely, but some perverse pthreads implementation
could change the order in which newly created threads are actually started.
If anyone thinks this is a problem, I can tweak it so that the test case
simply verifies that reasonable output is produced and another test can
verify that the two child thread numbers are actually different.

gdb/testsuite/ChangeLog:
    
    	* gdb.python/py-thrhandle.c, gdb.python/py-thrhandle.exp: New
    	files.
---
 gdb/testsuite/gdb.python/py-thrhandle.c   | 71 +++++++++++++++++++++++++++++++
 gdb/testsuite/gdb.python/py-thrhandle.exp | 46 ++++++++++++++++++++
 2 files changed, 117 insertions(+)

diff --git a/gdb/testsuite/gdb.python/py-thrhandle.c b/gdb/testsuite/gdb.python/py-thrhandle.c
new file mode 100644
index 0000000..ec148c9
--- /dev/null
+++ b/gdb/testsuite/gdb.python/py-thrhandle.c
@@ -0,0 +1,71 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2016 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see  <http://www.gnu.org/licenses/>.  */
+
+#include <stdio.h>
+#include <pthread.h>
+#include <unistd.h>
+#include <alloca.h>
+
+#define NTHR 3
+pthread_t thrs[NTHR];
+pthread_barrier_t barrier;
+pthread_mutex_t mutex;
+
+void
+do_something (int n)
+{
+  pthread_mutex_lock (&mutex);
+  printf ("%d\n", n);
+  pthread_mutex_unlock (&mutex);
+}
+
+void *
+do_work (void *data)
+{
+  int num = * (int *) data;
+
+  pthread_barrier_wait (&barrier);
+
+  do_something (num);
+
+  pthread_exit (NULL);
+}
+
+int
+main (int argc, char **argv)
+{
+  int i;
+
+  pthread_barrier_init (&barrier, NULL, NTHR-1);
+  pthread_mutex_init (&mutex, NULL);
+
+  thrs[0] = pthread_self ();
+
+  for (i=1; i< NTHR; i++)
+    {
+      int *iptr = alloca (sizeof (int));
+      
+      *iptr = i;
+      pthread_create (&thrs[i], NULL, do_work, iptr);
+    }
+
+  for (i=1; i< NTHR; i++)
+    {
+      pthread_join (thrs[i], NULL);
+    }
+  printf ("Done!");
+}
diff --git a/gdb/testsuite/gdb.python/py-thrhandle.exp b/gdb/testsuite/gdb.python/py-thrhandle.exp
new file mode 100644
index 0000000..a324d4e
--- /dev/null
+++ b/gdb/testsuite/gdb.python/py-thrhandle.exp
@@ -0,0 +1,46 @@
+# Copyright (C) 2016 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# Please email any bugs, comments, and/or additions to this file to:
+# bug-gdb@gnu.org
+
+# This file verifies that gdb.thread_from_thread_handle works as expected.
+
+standard_testfile
+
+
+if {[gdb_compile_pthreads "${srcdir}/${subdir}/${srcfile}" "${binfile}" executable debug] != "" } {
+    return -1
+}
+
+clean_restart ${binfile}
+runto_main
+
+gdb_test "break do_something" \
+    "Breakpoint 2 at .*: file .*${srcfile}, line .*" \
+         "breakpoint on do_something"
+
+gdb_test "continue" \
+	"Breakpoint 2, do_something .*" \
+	"run to do_something"
+
+gdb_test "python print gdb.thread_from_thread_handle(gdb.parse_and_eval('thrs\[0\]')).num" \
+	"1" 
+
+gdb_test "python print gdb.thread_from_thread_handle(gdb.parse_and_eval('thrs\[1\]')).num" \
+	"2"
+
+gdb_test "python print gdb.thread_from_thread_handle(gdb.parse_and_eval('thrs\[2\]')).num" \
+	"3"