Add build setting for enabling C++ interoperability#6276
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neonichu
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This adds a build setting to the package manifest that enables Swift/C++ Interoperability for a given Swift target: ``` .interoperabilityMode(.Cxx, version: "swift-5.9") ``` This relies on the new Swift driver flag for versioned C++ interop (see swiftlang/swift#64088). rdar://106756067
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Motivation:
When importing C language dependencies, the Swift compiler internally runs Clang in C/Objective-C mode by default.
If some of the imported clang modules are actually written in C++, that causes build errors since C++ syntax might be invalid in C/Objective-C. To resolve that, Swift allows the user to explicitly enable C++/Objective-C++ language mode (along with the rest of the Swift/C++ interoperability logic) for clang via a compiler flag. The reason we cannot enable C++/Objective-C++ mode by default is because it changes the way some existing C/Objective-C APIs are imported: for instance, a library header might provide a different definition of a symbol under
#ifdef __cplusplus.The user should be able to enable Swift/C++ interoperability for a given Swift target without using unsafe flags.
Modifications:
This adds a build setting to the package manifest that enables Swift/C++ Interoperability for a given Swift target:
The implementation relies on the new Swift driver flag for versioned C++ interop (see swiftlang/swift#64088).