lib: remove plugin's ABI version

We don't need this version property.

We intend for Babeltrace 2.y to be able to load any plugin written for
Babeltrace 2.x, where y ≥ x.

With this patch, `struct __bt_plugin_descriptor` only contains the
plugin's name, because this is the only required property. Optional
properties are within an array of plugin descriptor attributes
(`struct __bt_plugin_descriptor_attribute`). Each plugin descriptor
attribute has a type (`enum __bt_plugin_descriptor_attribute_type`), so
this is how we can introduce new, optional plugin properties, instead of
relying on some ABI version.

The same goes for component class attributes
(`struct __bt_plugin_component_class_descriptor_attribute`) and their
type
(`enum __bt_plugin_component_class_descriptor_attribute_type`).

Signed-off-by: Philippe Proulx <eeppeliteloop@gmail.com>
Change-Id: I4e9658f7d2216f43d872e3acd072dbdf588abe46
Reviewed-on: https://review.lttng.org/c/babeltrace/+/2220
Tested-by: jenkins <jenkins@lttng.org>
Reviewed-by: Francis Deslauriers <francis.deslauriers@efficios.com>

include/babeltrace2/plugin/plugin-dev.h

@@ -50,13 +50,6 @@
 extern "C" {
 #endif
 
-/*
- * Plugin interface's version, not synced with Babeltrace's version
- * (internal use).
- */
-#define __BT_PLUGIN_VERSION_MAJOR	1
-#define __BT_PLUGIN_VERSION_MINOR	0
-
 /* Plugin initialization function type */
 typedef enum bt_plugin_initialize_func_status {
 	BT_PLUGIN_INITIALIZE_FUNC_STATUS_OK		= __BT_FUNC_STATUS_OK,
@@ -72,12 +65,6 @@ typedef void (*bt_plugin_finalize_func)(void);
 
 /* Plugin descriptor: describes a single plugin (internal use) */
 struct __bt_plugin_descriptor {
-	/* Plugin's interface major version number */
-	uint32_t major;
-
-	/* Plugin's interface minor version number */
-	uint32_t minor;
-
 	/* Plugin's name */
 	const char *name;
 } __attribute__((packed));
@@ -433,8 +420,6 @@ struct __bt_plugin_component_class_descriptor_attribute const * const *__bt_get_
  */
 #define BT_PLUGIN_WITH_ID(_id, _name)					\
 	struct __bt_plugin_descriptor __bt_plugin_descriptor_##_id = {	\
-		.major = __BT_PLUGIN_VERSION_MAJOR,			\
-		.minor = __BT_PLUGIN_VERSION_MINOR,			\
 		.name = _name,						\
 	};								\
 	static struct __bt_plugin_descriptor const * const __bt_plugin_descriptor_##_id##_ptr __BT_PLUGIN_DESCRIPTOR_ATTRS = &__bt_plugin_descriptor_##_id

src/lib/plugin/plugin-so.c

@@ -1336,25 +1336,8 @@ int bt_plugin_so_create_all_from_sections(
 			continue;
 		}
 
-		BT_LOGI("Creating plugin object for plugin: "
-			"name=\"%s\", abi-major=%d, abi-minor=%d",
-			descriptor->name, descriptor->major, descriptor->minor);
-
-		if (descriptor->major > __BT_PLUGIN_VERSION_MAJOR) {
-			if (fail_on_load_error) {
-				BT_LIB_LOGW_APPEND_CAUSE(
-					"Unknown ABI major version: abi-major=%d",
-						descriptor->major);
-				status = BT_FUNC_STATUS_ERROR;
-				goto error;
-			} else {
-				BT_LIB_LOGW(
-					"Unknown ABI major version: abi-major=%d",
-						descriptor->major);
-				continue;
-			}
-		}
-
+		BT_LOGI("Creating plugin object for plugin: name=\"%s\"",
+			descriptor->name);
 		plugin = bt_plugin_so_create_empty(shared_lib_handle);
 		if (!plugin) {
 			BT_LIB_LOGE_APPEND_CAUSE(