gdb/python: New InferiorThread.ptid_string attribute

This commit adds a new InferiorThread.ptid_string attribute.  This
read-only attribute contains the string returned by target_pid_to_str,
which actually converts a ptid (not pid) to a string.

This is the string that appears (at least in part) in the output of
'info threads' in the 'Target Id' column, but also in the thread
exited message that GDB prints.

Having access to this string from Python is useful for allowing
extensions identify threads in a similar way to how GDB core would
identify the thread.

Reviewed-By: Eli Zaretskii <eliz@gnu.org>
Approved-By: Tom Tromey <tom@tromey.com>

gdb/NEWS

@@ -91,6 +91,10 @@ show remote thread-options-packet
   ** New function gdb.interrupt(), that interrupts GDB as if the user
      typed control-c.
 
+  ** New gdb.InferiorThread.ptid_string attribute.  This read-only
+     attribute contains the string that appears in the 'Target Id'
+     column of the 'info threads' command output.
+
 * Debugger Adapter Protocol changes
 
   ** GDB now emits the "process" event.

gdb/doc/python.texi

@@ -4084,6 +4084,13 @@ Either the LWPID or TID may be 0, which indicates that the operating system
 does not  use that identifier.
 @end defvar
 
+@defvar InferiorThread.ptid_string
+This read-only attribute contains a string representing
+@code{InferiorThread.ptid}.  This is the string that @value{GDBN} uses
+in the @samp{Target Id} column in the @kbd{info threads} output
+(@pxref{info_threads,,@samp{info threads}}).
+@end defvar
+
 @defvar InferiorThread.inferior
 The inferior this thread belongs to.  This attribute is represented as
 a @code{gdb.Inferior} object.  This attribute is not writable.

gdb/python/py-infthread.c

@@ -185,6 +185,30 @@ thpy_get_ptid (PyObject *self, void *closure)
   return gdbpy_create_ptid_object (thread_obj->thread->ptid);
 }
 
+/* Implement gdb.InferiorThread.ptid_string attribute.  */
+
+static PyObject *
+thpy_get_ptid_string (PyObject *self, void *closure)
+{
+  thread_object *thread_obj = (thread_object *) self;
+  THPY_REQUIRE_VALID (thread_obj);
+  ptid_t ptid = thread_obj->thread->ptid;
+
+  try
+    {
+      /* Select the correct inferior before calling a target_* function.  */
+      scoped_restore_current_thread restore_thread;
+      switch_to_inferior_no_thread (thread_obj->thread->inf);
+      std::string ptid_str = target_pid_to_str (ptid);
+      return PyUnicode_FromString (ptid_str.c_str ());
+    }
+  catch (const gdb_exception &except)
+    {
+      GDB_PY_HANDLE_EXCEPTION (except);
+      return nullptr;
+    }
+}
+
 /* Getter for InferiorThread.inferior -> Inferior.  */
 
 static PyObject *
@@ -388,6 +412,9 @@ static gdb_PyGetSetDef thread_object_getset[] =
     "Global number of the thread, as assigned by GDB.", NULL },
   { "ptid", thpy_get_ptid, NULL, "ID of the thread, as assigned by the OS.",
     NULL },
+  { "ptid_string", thpy_get_ptid_string, nullptr,
+    "A string representing ptid, as used by, for example, 'info threads'.",
+    nullptr },
   { "inferior", thpy_get_inferior, NULL,
     "The Inferior object this thread belongs to.", NULL },
 

gdb/testsuite/gdb.python/py-infthread.exp

@@ -62,6 +62,14 @@ gdb_test "python print ('result = %s' % t0.num)" " = 1" "test InferiorThread.num
 gdb_test "python print ('result = %s' % t0.global_num)" " = 1" "test InferiorThread.global_num"
 gdb_test "python print ('result = %s' % str (t0.ptid))" " = \\(\[0-9\]+, \[0-9\]+, \[0-9\]+\\)" "test InferiorThread.ptid"
 
+# Test the InferiorThread.ptid_string attribute.  We don't test the
+# actual string contents as they vary based on target, but we check
+# that we get back a non-empty string.
+gdb_test "python print(type(t0.ptid_string))" "<class 'str'>" \
+    "check that InferiorThread.ptid_string is a string"
+gdb_test "python print(t0.ptid_string)" ".+" \
+    "check that InferiorThread.ptid_string is non-empty"
+
 gdb_py_test_silent_cmd "python i0 = t0.inferior" "test InferiorThread.inferior" 1
 gdb_test "python print ('result = %s' % i0.num)" " = 1" "test Inferior.num"