From 4295ae96cdf275cdda8bded9271960a4cac11fb2 Mon Sep 17 00:00:00 2001 From: Jan Svoboda Date: Mon, 1 Mar 2021 18:52:15 +0100 Subject: [clang][modules] Use extensible RTTI for ModuleFileExtension Clang exposes an interface for extending the PCM/PCH file format: `ModuleFileExtension`. Clang itself has only a single implementation of the interface: `TestModuleFileExtension` that can be instantiated via the `-ftest-module-file_extension=` command line argument (and is stored in `FrontendOptions::ModuleFileExtensions`). Clients of the Clang library can extend the PCM/PCH file format by pushing an instance of their extension class to the `FrontendOptions::ModuleFileExtensions` vector. When generating the `-ftest-module-file_extension=` command line argument from `FrontendOptions`, a downcast is used to distinguish between the Clang's testing extension and other (client) extensions. This functionality is enabled by LLVM-style RTTI. However, this style of RTTI is hard to extend, as it requires patching Clang (adding new case to the `ModuleFileExtensionKind` enum). This patch switches to the LLVM RTTI for open class hierarchies, which allows libClang users (e.g. Swift) to create implementations of `ModuleFileExtension` without patching Clang. (Documentation of the feature: https://llvm.org/docs/HowToSetUpLLVMStyleRTTI.html#rtti-for-open-class-hierarchies) Reviewed By: artemcm Differential Revision: https://reviews.llvm.org/D97702 --- clang/lib/Frontend/TestModuleFileExtension.cpp | 2 ++ 1 file changed, 2 insertions(+) (limited to 'clang/lib/Frontend/TestModuleFileExtension.cpp') diff --git a/clang/lib/Frontend/TestModuleFileExtension.cpp b/clang/lib/Frontend/TestModuleFileExtension.cpp index ec147e1..7d4026a 100644 --- a/clang/lib/Frontend/TestModuleFileExtension.cpp +++ b/clang/lib/Frontend/TestModuleFileExtension.cpp @@ -15,6 +15,8 @@ using namespace clang; using namespace clang::serialization; +char TestModuleFileExtension::ID = 0; + TestModuleFileExtension::Writer::~Writer() { } void TestModuleFileExtension::Writer::writeExtensionContents( -- cgit v1.1