[WIP] Enable support for the @_section experimental attribute.
#210
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@swift-ci please test |
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This PR adds a `swift5_tests` property to `MetadataSections` and populates it in the static constructors used on Linux and Windows. This section will be used by swift-testing to store test metadata for discovery at runtime (see apple/swift-testing#210.) This change is necessary because on Linux and Windows, section boundaries are not discoverable at runtime and so must be noted on a per-image basis at compile time. (This is also why `MetadataSections` and the static constructors are present in the first place.) There are no compiler changes needed here. The compiler does not need special knowledge of the tests section emitted by swift-testing. The compiler does not itself need to emit anything into this section. This change does not affect platforms that use the Mach-O binary format (i.e. Darwin) because on those platforms, there is API to find sections and segments at runtime.
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@compnerd says the Windows section needs the suffix |
compnerd
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Linux failure is expected right now; the new |
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Looks like Windows has a compile-time complaint about the constness of C function pointers. |
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This PR enables support for `@_used` and `@_section` to allow embedding test data directly into its own section in a binary. This means we don't have to look up synthesized test types at runtime. Limitations: 1. Test clients must enable support for the experimental `"SymbolLinkageMarkers"` feature. 1. The `@_section` attribute currently doesn't support application to constants of function type, thinking they are non-constant. 1. We will need to make a change to the Swift runtime on Linux/Windows to add the new section to `MetadataSections` (or alternatively, the experimental feature needs to provide a different way to discover sections at runtime.) 1. We will need to make a change to the Swift compiler on Linux/Windows to ensure that the aforementioned section is always emitted since section discovery on those platforms is based on static linkage of the section boundary symbols (so if they're not present, a linker error will occur.) :warning: Do not merge: this is a proof-of-concept and work-in-progress.
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This PR enables support for
@_usedand@_sectionto allow embedding test data directly into its own section in a binary. This means we don't have to look up synthesized test types at runtime.Limitations:
"SymbolLinkageMarkers"feature.@_sectionattribute currently doesn't support application to constants of function type, thinking they are non-constant.MetadataSections(or alternatively, the experimental feature needs to provide a different way to discover sections at runtime.) See Addswift5_teststoMetadataSections. swift#71509.Checklist: