[clang] True `noexcept` (`-fstrict-noexcept` language dialect)
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Authored by lebedev.ri on Jan 11 2023, 6:06 PM.

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Reviewers

aaron.ballman
rjmccall
efriedma
jcranmer
jyknight
rsmith

Summary

This tentatively implements the following RFC:
https://discourse.llvm.org/t/rfc-clang-true-noexcept-aka-defaults-are-often-wrong-hardcoded-defaults-are-always-wrong/67629

The idea is that when the opt-in is specified,
we turn all EH Terminate scopes into EH UB scopes,
and don't emit any std::terminate() calls,
which is the user-facing change.

This probably needs better docs,
and might be missing some pieces.

We might be able to do more to omit more destructor calls.

This is missing UBSan bits, those will be in D137381.

Diff Detail

Repository: rG LLVM Github Monorepo

Unit TestsFailed
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	Time	Test
	3,720 ms	libcxx CI Modules > llvm-libc++-shared-cfg-in.libcxx/algorithms/specialized_algorithms/special_mem_concepts::nothrow_sentinel_for.compile.pass.cpp Script: -- : 'COMPILED WITH'; /home/libcxx-builder/.buildkite-agent/builds/5decb14811a9-1/llvm-project/libcxx-ci/install/bin/clang++ /home/libcxx-builder/.buildkite-agent/builds/5decb14811a9-1/llvm-project/libcxx-ci/libcxx/test/libcxx/algorithms/specialized.algorithms/special.mem.concepts/nothrow_sentinel_for.compile.pass.cpp --target=x86_64-unknown-linux-gnu -nostdinc++ -I /home/libcxx-builder/.buildkite-agent/builds/5decb14811a9-1/llvm-project/libcxx-ci/build/generic-modules/include/c++/v1 -I /home/libcxx-builder/.buildkite-agent/builds/5decb14811a9-1/llvm-project/libcxx-ci/build/generic-modules/include/c++/v1 -I /home/libcxx-builder/.buildkite-agent/builds/5decb14811a9-1/llvm-project/libcxx-ci/libcxx/test/support -std=c++2b -fmodules -fcxx-modules -Werror -Wall -Wctad-maybe-unsupported -Wextra -Wshadow -Wundef -Wno-unused-command-line-argument -Wno-attributes -Wno-pessimizing-move -Wno-c++11-extensions -Wno-noexcept-type -Wno-atomic-alignment -Wno-user-defined-literals -Wno-tautological-compare -Wsign-compare -Wunused-variable -Wunused-parameter -Wunreachable-code -Wno-unused-local-typedef -D_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER -D_LIBCPP_ENABLE_EXPERIMENTAL -D_LIBCPP_DISABLE_AVAILABILITY -fcoroutines-ts -Werror=thread-safety -Wuser-defined-warnings -fsyntax-only

Event Timeline

lebedev.ri created this revision.Jan 11 2023, 6:06 PM

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lebedev.ri requested review of this revision.Jan 11 2023, 6:06 PM

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Harbormaster completed remote builds in B207259: Diff 488447.Jan 11 2023, 8:10 PM

Effectively ignore dynamic exception specifications.
Normally, they'd catch, filter and either abort or resume.
But just skipping the abort part still leaves us with the rest of
the gunk that we fail to optimize away later: https://godbolt.org/z/vh58E4ooG

Harbormaster completed remote builds in B207425: Diff 488677.Jan 12 2023, 10:53 AM

ChuanqiXu added a subscriber: ChuanqiXu.Jan 12 2023, 6:40 PM

Adding more docs as discussed. Further suggestions welcomed.

Harbormaster completed remote builds in B208371: Diff 489992.Jan 17 2023, 7:13 PM