Allow C targets to import the compatibility header generated for Swift libraries #8736
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The module map generated for the compatibility header was marked as `requires objc`. This triggers an error when importing it from a C source file. This declaration is superfluous, the compatibility header is already printed in a way where the Objective-C code is protected behind a language check. C clients can safely import the current compatibility header even if it may not see any content. Let's lift this restriction. It isn't currently necessary and we're adding C content to the compatibility header with the official support for `@cdecl` that is independent of Objective-C.
…tory Emit the generated compatibility header and module map in a new `include` directory under the temporary build directory of Swift libraries. This directory can then be used as a header search path for the dependent clang targets. This replaces the previous header search strategy that used only the generated module map. This was incompatible with C source files and classic non-module textual includes. The use of a header search path should support both module imports via the module map as well as includes of the compatibility header.
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jakepetroules,
dschaefer2,
shawnhyam,
bripeticca,
plemarquand,
owenv,
bkhouri,
cmcgee1024 and
daveyc123
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@swift-ci Please test |
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@swift-ci Please test macOS |
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@swift-ci Please test |
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@swift-ci Please test Windows |
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@swift-ci Please test |
Also lift the macOS restriction now that swiftpm emits the compatibility header on other platforms.
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@swift-ci Please test |
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@swift-ci Please test Windows |
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Is someone available to review this change? |
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@jakepetroules do you think we need a similar change in swift-build? It appears to print the |
I think so, yeah, at least for the |
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Address two issues preventing a C source file to import the generated compatibility header:
Don't mark the module map generated for the compatibility header as
requires objc. This triggers an error when importing it from a C source file. The compatibility header is already printed in a way where the Objective-C code is protected behind a language check. C clients can safely import it even if they may not see any content. Plus we're adding C content to the compatibility header with the official support for@cdeclthat is independent of Objective-C.Emit the generated compatibility header and module map in a new
includedirectory under the temporary build directory of each Swift library. This directory is then used as a header search path for the dependent clang targets.This replaces the previous strategy that relied only the generated module map to resolve imports. It was incompatible with C source files and non-modular textual includes. The use of a header search path preserves the support for module imports via the same module map and supports textual includes of the compatibility header.
Fixes #7257.
Follow up to #8695.