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This patch removes some vendor-specific availability XFAILs from the test suite. In the future, when a new feature is introduced in the dylib, an availability macro should be created and a matching lit feature should be created. That way, the test suite can XFAIL whenever the implementation lacks the necessary feature instead of being cluttered by vendor-specific annotations. Right now, those vendor-specific annotations are still somewhat cluttering the test suite by being in `config.py`, but at least they are localized. In the future, we could design a way to define those less intrusively or even automatically based on the availability macros that already exist in <__config>. llvm-svn: 353201
106 lines
4.2 KiB
ReStructuredText
106 lines
4.2 KiB
ReStructuredText
===================
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Availability Markup
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===================
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.. contents::
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:local:
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Overview
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========
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Libc++ is used as a system library on macOS and iOS (amongst others). In order
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for users to be able to compile a binary that is intended to be deployed to an
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older version of the platform, clang provides the
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`availability attribute <https://clang.llvm.org/docs/AttributeReference.html#availability>`_
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that can be placed on declarations to describe the lifecycle of a symbol in the
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library.
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Design
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======
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When a new feature is introduced that requires dylib support, a macro should be
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created in include/__config to mark this feature as unavailable for all the
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systems. For example::
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// Define availability macros.
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#if defined(_LIBCPP_USE_AVAILABILITY_APPLE)
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# define _LIBCPP_AVAILABILITY_BAD_OPTIONAL_ACCESS __attribute__((unavailable))
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#else if defined(_LIBCPP_USE_AVAILABILITY_SOME_OTHER_VENDOR)
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# define _LIBCPP_AVAILABILITY_BAD_OPTIONAL_ACCESS __attribute__((unavailable))
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#else
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# define _LIBCPP_AVAILABILITY_BAD_OPTIONAL_ACCESS
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#endif
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When the library is updated by the platform vendor, the markup can be updated.
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For example::
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#define _LIBCPP_AVAILABILITY_SHARED_MUTEX \
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__attribute__((availability(macosx,strict,introduced=10.12))) \
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__attribute__((availability(ios,strict,introduced=10.0))) \
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__attribute__((availability(tvos,strict,introduced=10.0))) \
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__attribute__((availability(watchos,strict,introduced=3.0)))
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In the source code, the macro can be added on a class if the full class requires
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type info from the library for example::
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_LIBCPP_BEGIN_NAMESPACE_EXPERIMENTAL
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class _LIBCPP_EXCEPTION_ABI _LIBCPP_AVAILABILITY_BAD_OPTIONAL_ACCESS bad_optional_access
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: public std::logic_error {
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or on a particular symbol:
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_LIBCPP_OVERRIDABLE_FUNC_VIS _LIBCPP_AVAILABILITY_SIZED_NEW_DELETE void operator delete(void* __p, std::size_t __sz) _NOEXCEPT;
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Furthermore, a lit feature should be added to match that availability macro,
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so that tests depending on that feature can be marked to XFAIL if the feature
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is not supported. This way, the test suite will work on platforms that have
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not shipped the feature yet. This can be done by adding the appropriate lit
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feature in test/config.py.
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Testing
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=======
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Some parameters can be passed to lit to run the test-suite and exercise the
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availability.
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* The `platform` parameter controls the deployment target. For example lit can
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be invoked with `--param=platform=macosx10.8`. Default is the current host.
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* The `use_system_cxx_lib` parameter indicates to use another library than the
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just built one. Invoking lit with `--param=use_system_cxx_lib=true` will run
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the test-suite against the host system library. Alternatively a path to the
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directory containing a specific prebuilt libc++ can be used, for example:
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`--param=use_system_cxx_lib=/path/to/macOS/10.8/`.
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Tests can be marked as XFAIL based on multiple features made available by lit:
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* if `--param=platform=macosx10.8` is passed, the following features will be available:
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- availability
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- availability=x86_64
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- availability=macosx
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- availability=x86_64-macosx
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- availability=x86_64-apple-macosx10.8
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- availability=macosx10.8
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This feature is used to XFAIL a test that *is* using a class or a method marked
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as unavailable *and* that is expected to *fail* if deployed on an older system.
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* if `use_system_cxx_lib` and `--param=platform=macosx10.8` are passed to lit,
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the following features will also be available:
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- with_system_cxx_lib
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- with_system_cxx_lib=x86_64
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- with_system_cxx_lib=macosx
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- with_system_cxx_lib=x86_64-macosx
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- with_system_cxx_lib=x86_64-apple-macosx10.8
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- with_system_cxx_lib=macosx10.8
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This feature is used to XFAIL a test that is *not* using a class or a method
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marked as unavailable *but* that is expected to fail if deployed on an older
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system. For example, if the test exhibits a bug in the libc on a particular
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system version, or if the test uses a symbol that is not available on an
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older version of the dylib (but for which there is no availability markup,
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otherwise the XFAIL should use `availability` above).
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