lib: Make bt_value_null a const pointer

We probably don't want anything to change the value of this pointer,
which points to the only instance of BT_VALUE_TYPE_NULL,
bt_value_null_instance.  Therefore, declare it as a constant value.

It also helps a little bit the Python bindings: if we copy the
declaration verbatim to the .i file, without const, bt_value_null is
available through the special "cvar" global object (and can be
modified!).  With const, it becomes read-only, so can be accessed
directly as native_bt.value_null.

Signed-off-by: Simon Marchi <simon.marchi@efficios.com>

diff --git a/include/babeltrace/value.h b/include/babeltrace/value.h
index 1e6bdc47c468b9398a0870d5e05a4b64fab323b5..89c4c64ef5311ea8b874c2d1d977a0017801b129 100644 (file)
--- a/include/babeltrace/value.h
+++ b/include/babeltrace/value.h
@@ -36,7 +36,7 @@
 extern "C" {
 #endif
 
-extern bt_value *bt_value_null;
+extern bt_value *const bt_value_null;
 
 extern bt_value *bt_value_bool_create(void);
 

diff --git a/lib/value.c b/lib/value.c
index eb78ca9ecd10b5ba975ad0776c4d4b47b9a9f852..83168e74fe9cd99c22922342a219684865a31feb 100644 (file)
--- a/lib/value.c
+++ b/lib/value.c
@@ -87,7 +87,7 @@ struct bt_value bt_value_null_instance = {
        .frozen = BT_TRUE,
 };
 
-struct bt_value *bt_value_null = &bt_value_null_instance;
+struct bt_value *const bt_value_null = &bt_value_null_instance;
 
 struct bt_value_bool {
        struct bt_value base;