Re-analyze functions as top-level
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Authored by chrisbazley on Jan 27 2023, 9:06 AM.

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Summary

If a function with a _Nullable parameter has at least
one caller, the checker behaves as though no other
parameter value is possible. This is because the static
analyzer doesn't re-analyse functions as top level
(with the exception of C++ copy and move operators, and
ObjC methods).

Fixed by modifying shouldSkipFunction to return false.

After this change, Clang-tidy even emits different
warnings for the same line of code, if appropriate:
"Nullable pointer is dereferenced" for a (simulated)
top-level call and "Dereference of null pointer"
for a call to the same function with a known null value.

Diff Detail

Repository: rG LLVM Github Monorepo

Unit TestsFailed
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	Time	Test
	3,470 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/b44fbc847e23-1/llvm-project/libcxx-ci/install/bin/clang++ /home/libcxx-builder/.buildkite-agent/builds/b44fbc847e23-1/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/b44fbc847e23-1/llvm-project/libcxx-ci/build/generic-modules/include/c++/v1 -I /home/libcxx-builder/.buildkite-agent/builds/b44fbc847e23-1/llvm-project/libcxx-ci/build/generic-modules/include/c++/v1 -I /home/libcxx-builder/.buildkite-agent/builds/b44fbc847e23-1/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 -Werror=thread-safety -Wuser-defined-warnings -fsyntax-only

Event Timeline

chrisbazley created this revision.Jan 27 2023, 9:06 AM

Herald added a reviewer: NoQ. · View Herald TranscriptJan 27 2023, 9:06 AM

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chrisbazley requested review of this revision.Jan 27 2023, 9:06 AM

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chrisbazley added a parent revision: D142743: Fix nullability checking of top-level functions.Jan 27 2023, 9:06 AM

This change is admittedly a hack. It might be better to check the function parameter types, or maybe the list of exceptions in this function is now so long that it no longer serves any purpose.

Harbormaster completed remote builds in B210391: Diff 492795.Jan 27 2023, 11:25 AM

Please refer to https://discourse.llvm.org/t/rfc-optional-a-type-qualifier-to-indicate-pointer-nullability/ and https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3089.pdf for the wider context of this commit.