fe59f72b9a
Consider the following code: ```cpp # 1 __FILE__ 1 3 export module a; ``` According to the wording in [P1857R3](https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2020/p1857r3.html): ``` A module directive may only appear as the first preprocessing tokens in a file (excluding the global module fragment.) ``` and the wording in [[cpp.pre]](https://eel.is/c++draft/cpp.pre#nt:module-file) ``` module-file: pp-global-module-fragment[opt] pp-module group[opt] pp-private-module-fragment[opt] ``` `#` is the first pp-token in the translation unit, and it was rejected by clang, but they really should be exempted from this rule. The goal is to not allow any preprocessor conditionals or most state changes, but these don't fit that. State change would mean most semantically observable preprocessor state, particularly anything that is order dependent. Global flags like being a system header/module shouldn't matter. We should exempt a brunch of directives, even though it violates the current standard wording. In this patch, we introduce a `TrivialDirectiveTracer` to trace the **State change** that described above and propose to exempt the following kind of directive: `#line`, GNU line marker, `#ident`, `#pragma comment`, `#pragma mark`, `#pragma detect_mismatch`, `#pragma clang __debug`, `#pragma message`, `#pragma GCC warning`, `#pragma GCC error`, `#pragma gcc diagnostic`, `#pragma OPENCL EXTENSION`, `#pragma warning`, `#pragma execution_character_set`, `#pragma clang assume_nonnull` and builtin macro expansion. Fixes https://github.com/llvm/llvm-project/issues/145274 --------- Signed-off-by: yronglin <yronglin777@gmail.com> (cherry picked from commit e6e874ce8f055f5b8c5d7f8c7fb0afe764d1d350)
C language Family Front-end
Welcome to Clang.
This is a compiler front-end for the C family of languages (C, C++ and Objective-C) which is built as part of the LLVM compiler infrastructure project.
Unlike many other compiler frontends, Clang is useful for a number of things beyond just compiling code: we intend for Clang to be host to a number of different source-level tools. One example of this is the Clang Static Analyzer.
If you're interested in more (including how to build Clang) it is best to read the relevant websites. Here are some pointers:
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Information on Clang: http://clang.llvm.org/
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Building and using Clang: http://clang.llvm.org/get_started.html
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Clang Static Analyzer: http://clang-analyzer.llvm.org/
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Information on the LLVM project: http://llvm.org/
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If you have questions or comments about Clang, a great place to discuss them is on the Clang forums:
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If you find a bug in Clang, please file it in the LLVM bug tracker: