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qt-build-utils: add a usage for qt_plugin_instance #1442

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qt-build-utils: add a usage for qt_plugin_instance #1442

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35 changes: 33 additions & 2 deletions crates/qt-build-utils/src/qml/qmlplugincpp.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -86,6 +86,35 @@ impl QmlPluginCppBuilder {
}
let declarations = declarations.join("\n");
let usages = usages.join("\n");
let dynamic_qt_plugin_usage = if self.plugin_type == PluginType::Dynamic {
r#"
// When exporting as a dynamic plugin we need to ensure that extern "C"
// functions from the moc generation of the plugin remain in the final output
//
// This mainly means that we need to ensure that QT_MOC_EXPORT_PLUGIN
// and QT_MOC_EXPORT_PLUGIN_V2 exports remain
//
// Both macros make use of QT_MOC_EXPORT_PLUGIN_COMMON
// which exports qt_plugin_instance
// https://code.qt.io/cgit/qt/qtbase.git/tree/src/corelib/plugin/qplugin.h?h=6.11.1#n244
volatile auto qt_plugin_instance_usage = &qt_plugin_instance;
Q_UNUSED(qt_plugin_instance_usage);

#ifdef QT_MOC_EXPORT_PLUGIN_V2
// QT_MOC_EXPORT_PLUGIN_V2 exports qt_plugin_query_metadata_v2
// https://code.qt.io/cgit/qt/qtbase.git/tree/src/corelib/plugin/qplugin.h?h=6.11.1#n255
volatile auto qt_plugin_query_metadata_v2_usage = &qt_plugin_query_metadata_v2;
Q_UNUSED(qt_plugin_query_metadata_v2_usage);
#else
// QT_MOC_EXPORT_PLUGIN exports qt_plugin_query_metadata
// https://code.qt.io/cgit/qt/qtbase.git/tree/src/corelib/plugin/qplugin.h?h=6.11.1#n249
volatile auto qt_plugin_query_metadata_usage = &qt_plugin_query_metadata;
Q_UNUSED(qt_plugin_query_metadata_usage);
#endif
"#
} else {
""
};
let init_fn_name = format!("init_cxx_qt_qml_module_{plugin_class_name}");
write!(
writer,
Expand All @@ -108,17 +137,19 @@ public:
}}
}};

// The moc-generated cpp file doesn't compile on its own; it needs to be #included here.
#include "moc_{plugin_class_name}.cpp.cpp"

extern "C" {{
// "drive-by initialization" causes the plugin class to be included in static linking scenarios
// Any function that is called from within this file causes the entire object file to be linked in.
// Therefore we provide an empty function that can be called at any point to ensure this file is linked in.
bool {init_fn_name}() {{
{dynamic_qt_plugin_usage}
return true;
}}
}}

// The moc-generated cpp file doesn't compile on its own; it needs to be #included here.
#include "moc_{plugin_class_name}.cpp.cpp"
"#
)?;
let initializer = match self.plugin_type {
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