gdb/python: add gdb.history_count function

Add a new function gdb.history_count to the Python api, this function
returns an integer, the number of items in GDB's value history.

This is useful if you want to pull items from the history by their
absolute number, for example, if you wanted to show a complete history
list.  Previously we could figure out how many items are in the
history list by trying to fetch the items, and then catching the
exception when the item is not available, but having this function
seems nicer.

3 files changed, 11 insertions, 0 deletions

diff --git a/gdb/python/py-value.c b/gdb/python/py-value.c
index d6ceb54..6401d96 100644
--- a/gdb/python/py-value.c
+++ b/gdb/python/py-value.c
@@ -2012,6 +2012,14 @@ gdbpy_add_history (PyObject *self, PyObject *args)
   return nullptr;
 }
 
+/* Return an integer, the number of items in GDB's history.  */
+
+PyObject *
+gdbpy_history_count (PyObject *self, PyObject *args)
+{
+  return gdb_py_object_from_ulongest (value_history_count ()).release ();
+}
+
 /* Return the value of a convenience variable.  */
 PyObject *
 gdbpy_convenience_variable (PyObject *self, PyObject *args)
diff --git a/gdb/python/python-internal.h b/gdb/python/python-internal.h
index ccea5c4..5e15f62 100644
--- a/gdb/python/python-internal.h
+++ b/gdb/python/python-internal.h
@@ -412,6 +412,7 @@ extern enum ext_lang_rc gdbpy_get_matching_xmethod_workers
 
 PyObject *gdbpy_history (PyObject *self, PyObject *args);
 PyObject *gdbpy_add_history (PyObject *self, PyObject *args);
+extern PyObject *gdbpy_history_count (PyObject *self, PyObject *args);
 PyObject *gdbpy_convenience_variable (PyObject *self, PyObject *args);
 PyObject *gdbpy_set_convenience_variable (PyObject *self, PyObject *args);
 PyObject *gdbpy_breakpoints (PyObject *, PyObject *);
diff --git a/gdb/python/python.c b/gdb/python/python.c
index 7ddc170..2c8081e 100644
--- a/gdb/python/python.c
+++ b/gdb/python/python.c
@@ -2212,6 +2212,8 @@ PyMethodDef python_GdbMethods[] =
     "Get a value from history" },
   { "add_history", gdbpy_add_history, METH_VARARGS,
     "Add a value to the value history list" },
+  { "history_count", gdbpy_history_count, METH_NOARGS,
+    "Return an integer, the number of values in GDB's value history" },
   { "execute", (PyCFunction) execute_gdb_command, METH_VARARGS | METH_KEYWORDS,
     "execute (command [, from_tty] [, to_string]) -> [String]\n\
 Evaluate command, a string, as a gdb CLI command.  Optionally returns\n\