BASE: Remove bad casts between incompatible Plugin types

Previously, a C-style cast was used to convert a
Common::Array<Plugin *>, populated with pointers to StaticPlugin
and DynamicPlugin instances, to a
Common::Array<PluginSubclass<T> *>, but PluginSubclass<T> is a
*sibling* class to StaticPlugin/DynamicPlugin, so this cast was
invalid and the results undefined. The methods for retrieving
subclasses of plugins can't be easily changed to just generate an
array of temporary wrapper objects that expose an identical API
which dereferences to the preferred PluginObject subclass because
pointers to these objects are retained by other parts of ScummVM,
so the wrappers would needed to be persisted or they would need to
just re-expose the underlying Plugin object again. This indicated
that a way to solve this problem is to have the callers receive
Plugin objects and get the PluginObject from the Plugin by
explicitly stating their desired type, in a similar manner to
std::get(std::variant), so that the pattern used by this patch to
solve the problem.

Closes gh-1051.

1 files changed, 12 insertions, 12 deletions

diff --git a/base/plugins.cpp b/base/plugins.cpp
index 39aaf2f73e..18755003b4 100644
--- a/base/plugins.cpp
+++ b/base/plugins.cpp
@@ -457,7 +457,7 @@ DECLARE_SINGLETON(EngineManager);
  * For the uncached version, we first try to find the plugin using the gameId
  * and only if we can't find it there, we loop through the plugins.
  **/
-GameDescriptor EngineManager::findGame(const Common::String &gameName, const EnginePlugin **plugin) const {
+GameDescriptor EngineManager::findGame(const Common::String &gameName, const Plugin **plugin) const {
 	GameDescriptor result;
 
 	// First look for the game using the plugins in memory. This is critical
@@ -493,18 +493,18 @@ GameDescriptor EngineManager::findGame(const Common::String &gameName, const Eng
 /**
  * Find the game within the plugins loaded in memory
  **/
-GameDescriptor EngineManager::findGameInLoadedPlugins(const Common::String &gameName, const EnginePlugin **plugin) const {
+GameDescriptor EngineManager::findGameInLoadedPlugins(const Common::String &gameName, const Plugin **plugin) const {
 	// Find the GameDescriptor for this target
-	const EnginePlugin::List &plugins = getPlugins();
+	const PluginList &plugins = getPlugins();
 	GameDescriptor result;
 
 	if (plugin)
 		*plugin = 0;
 
-	EnginePlugin::List::const_iterator iter;
+	PluginList::const_iterator iter;
 
 	for (iter = plugins.begin(); iter != plugins.end(); ++iter) {
-		result = (**iter)->findGame(gameName.c_str());
+		result = (*iter)->get<MetaEngine>().findGame(gameName.c_str());
 		if (!result.gameid().empty()) {
 			if (plugin)
 				*plugin = *iter;
@@ -516,22 +516,22 @@ GameDescriptor EngineManager::findGameInLoadedPlugins(const Common::String &game
 
 GameList EngineManager::detectGames(const Common::FSList &fslist) const {
 	GameList candidates;
-	EnginePlugin::List plugins;
-	EnginePlugin::List::const_iterator iter;
+	PluginList plugins;
+	PluginList::const_iterator iter;
 	PluginManager::instance().loadFirstPlugin();
 	do {
 		plugins = getPlugins();
 		// Iterate over all known games and for each check if it might be
 		// the game in the presented directory.
 		for (iter = plugins.begin(); iter != plugins.end(); ++iter) {
-			candidates.push_back((**iter)->detectGames(fslist));
+			candidates.push_back((*iter)->get<MetaEngine>().detectGames(fslist));
 		}
 	} while (PluginManager::instance().loadNextPlugin());
 	return candidates;
 }
 
-const EnginePlugin::List &EngineManager::getPlugins() const {
-	return (const EnginePlugin::List &)PluginManager::instance().getPlugins(PLUGIN_TYPE_ENGINE);
+const PluginList &EngineManager::getPlugins() const {
+	return PluginManager::instance().getPlugins(PLUGIN_TYPE_ENGINE);
 }
 
 
@@ -543,6 +543,6 @@ namespace Common {
 DECLARE_SINGLETON(MusicManager);
 }
 
-const MusicPlugin::List &MusicManager::getPlugins() const {
-	return (const MusicPlugin::List &)PluginManager::instance().getPlugins(PLUGIN_TYPE_MUSIC);
+const PluginList &MusicManager::getPlugins() const {
+	return PluginManager::instance().getPlugins(PLUGIN_TYPE_MUSIC);
 }