CMake: Support CMP0157 when available#3321
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CMP0157 (introduced in CMake 3.29) improves Swift support in CMake by handling many build details natively instead of requiring manual configuration. It also introduces an abstraction for selecting the Swift compilation mode per target. Supporting CMP0157 will simplify the Swift toolchain build once the necessary changes have landed in the main Swift repository. These changes make it possible to support CMP0157 set to either OLD or NEW. We cannot yet require CMP0157 to be NEW, because the Swift compiler build (which consumes swift-syntax via FetchContent) has not yet adopted the policy. When the parent project's policy is OLD, swift-syntax falls back to the legacy code path. The OLD support should be removed once the Swift-repo-side changes have landed.
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@swift-ci please test |
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CMake 3.29 introduces CMP0157, which improves Swift support in CMake. These changes require swiftlang/swift-syntax#3321 to work properly as swift-syntax does not build with CMP0157 set to NEW otherwise.
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@etcwilde would you review this? |
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CMP0157 (introduced in CMake 3.29) improves Swift support in CMake by handling many build details natively instead of requiring manual configuration. It also introduces an abstraction for selecting the Swift compilation mode per target.
Supporting CMP0157 will simplify the Swift toolchain build once the necessary changes have landed in the main Swift repository.
These changes make it possible to support CMP0157 set to either OLD or NEW. We cannot yet require CMP0157 to be NEW, because the Swift compiler build (which consumes swift-syntax via FetchContent) has not yet adopted the policy. When the parent project's policy is OLD, swift-syntax falls back to the legacy code path. The OLD support should be removed once the Swift-repo-side changes have landed.
These changes unblock further upgrades to CMake, which are currently blocked behind support for CMP0157, and changes to the way linker flags are passed to Swift, starting with CMake 3.30.
There should be no changes in the built artifacts, whether CMP0157 is set to OLD or NEW.
Minimal. The changes were tested locally and will be tested on CI.
Local testing + CI.