[PATCH] D97702: [clang][modules] Use extensible RTTI for ModuleFileExtension

[Jan Svoboda via Phabricator via cfe-commits]

jansvoboda11 created this revision.
jansvoboda11 added reviewers: Bigcheese, dexonsmith.
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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 adding their implementation of the interface to `FrontendOptions::ModuleFileExtensions`.

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.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D97702

Files:
  clang/include/clang/Serialization/ModuleFileExtension.h
  clang/lib/Frontend/TestModuleFileExtension.cpp
  clang/lib/Frontend/TestModuleFileExtension.h
  clang/lib/Serialization/ModuleFileExtension.cpp
  clang/unittests/Frontend/CompilerInvocationTest.cpp

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