llvm-project

05805632 - [llvm] annotate interfaces in llvm-c for DLL export (#141701)

[llvm] annotate interfaces in llvm-c for DLL export (#141701) ## Purpose This patch is one in a series of code-mods that annotate LLVM’s public interface for export. This patch annotates the `llvm-c` interface with a new `LLVM_C_ABI` annotation, which behaves like the `LLVM_ABI`. This annotation currently has no meaningful impact on the LLVM build; however, it is a prerequisite to support an LLVM Windows DLL (shared library) build. ## Overview 1. Add a new `llvm-c/Visibility.h` header file that defines a new `LLVM_C_ABI` macro. The macro resolves to the proper DLL export/import annotation on Windows and a "default" visibility annotation elsewhere. 2. Add a new `LLVM_ENABLE_LLVM_C_EXPORT_ANNOTATIONS` `#cmakedefine` that is used to gate the definition of `LLVM_C_ABI`. 3. Remove the existing `LLVM_C_ABI` definition from `llvm/Support/Compiler.h`. Update the small number of `LLVM_C_ABI` references to get it from the new `llvm-c/Visibility.h` header. 4. Code-mod annotate the public `llvm-c` interface using the [Interface Definition Scanner (IDS)](https://github.com/compnerd/ids) tool. 5. Format the changes with `clang-format`. ## Background This effort is tracked in #109483. Additional context is provided in [this discourse](https://discourse.llvm.org/t/psa-annotating-llvm-public-interface/85307), and documentation for `LLVM_ABI` and related annotations is found in the LLVM repo [here](https://github.com/llvm/llvm-project/blob/main/llvm/docs/InterfaceExportAnnotations.rst). ## Validation Local builds and tests to validate cross-platform compatibility. This included llvm, clang, and lldb on the following configurations: - Windows with MSVC - Windows with Clang - Linux with GCC - Linux with Clang - Darwin with Clang