Author: Arseniy Zaostrovnykh Date: 2025-01-20T10:02:57+01:00 New Revision: d049db83627d164e4353f59a5f0b4f87dd74b138
URL: https://github.com/llvm/llvm-project/commit/d049db83627d164e4353f59a5f0b4f87dd74b138 DIFF: https://github.com/llvm/llvm-project/commit/d049db83627d164e4353f59a5f0b4f87dd74b138.diff LOG: [clang] Fix false warning on reinterpret_casting unknown template type (#109430) After 1595988ee6f9732e7ea79928af8a470ad5ef7dbe diag::warn_undefined_reinterpret_cast started raising on non-instantiated template functions without sufficient knowledge whether the reinterpret_cast is indeed UB. Added: Modified: clang/docs/ReleaseNotes.rst clang/lib/Sema/SemaCast.cpp clang/test/SemaCXX/reinterpret-cast.cpp Removed: ################################################################################ diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst index 2f7b9227386961..f6d5c346021d60 100644 --- a/clang/docs/ReleaseNotes.rst +++ b/clang/docs/ReleaseNotes.rst @@ -660,6 +660,8 @@ Improvements to Clang's diagnostics - Don't emit bogus dangling diagnostics when ``[[gsl::Owner]]`` and `[[clang::lifetimebound]]` are used together (#GH108272). +- Don't emit bogus dignostic about an undefined behavior on ``reinterpret_cast<T>`` for non-instantiated template functions without sufficient knowledge whether it can actually lead to undefined behavior for ``T`` (#GH109430). + - The ``-Wreturn-stack-address`` warning now also warns about addresses of local variables passed to function calls using the ``[[clang::musttail]]`` attribute. diff --git a/clang/lib/Sema/SemaCast.cpp b/clang/lib/Sema/SemaCast.cpp index f98857f852b5af..54bc52fa2ac405 100644 --- a/clang/lib/Sema/SemaCast.cpp +++ b/clang/lib/Sema/SemaCast.cpp @@ -2094,6 +2094,10 @@ void Sema::CheckCompatibleReinterpretCast(QualType SrcType, QualType DestType, } } + if (SrcTy->isDependentType() || DestTy->isDependentType()) { + return; + } + Diag(Range.getBegin(), DiagID) << SrcType << DestType << Range; } diff --git a/clang/test/SemaCXX/reinterpret-cast.cpp b/clang/test/SemaCXX/reinterpret-cast.cpp index 45332fd15b5d4e..bfb808773b9004 100644 --- a/clang/test/SemaCXX/reinterpret-cast.cpp +++ b/clang/test/SemaCXX/reinterpret-cast.cpp @@ -302,3 +302,77 @@ void reinterpret_cast_allowlist () { (void)reinterpret_cast<unsigned char&>(b); (void)*reinterpret_cast<unsigned char*>(&b); } + +namespace templated { +template <typename TARGETTYPE, typename UATYPE> +void cast_uninstantiated() { + const UATYPE* data; + (void)*reinterpret_cast<const TARGETTYPE*>(data); // no warning +} + + +template <typename TARGETTYPE, typename UATYPE> +void cast_instantiated_badly() { + const UATYPE* data; + (void)*reinterpret_cast<const TARGETTYPE*>(data); // expected-warning {{dereference of type 'const int *' that was reinterpret_cast from type 'const float *' has undefined behavior}} +} + +template <typename TARGETTYPE, typename UATYPE> +void cast_instantiated_well() { + const UATYPE* data; + (void)*reinterpret_cast<const TARGETTYPE*>(data); // no warning +} + +template <typename TARGETTYPE> +void cast_one_tmpl_arg_uninstantiated() { + const int* data; + (void)*reinterpret_cast<const TARGETTYPE*>(data); // no warning +} + +template <typename TARGETTYPE> +void cast_one_tmpl_arg_instantiated_badly() { + const float* data; + (void)*reinterpret_cast<const TARGETTYPE*>(data); // expected-warning {{dereference of type 'const int *' that was reinterpret_cast from type 'const float *' has undefined behavior}} +} + +template <typename TARGETTYPE> +void cast_one_tmpl_arg_instantiated_well() { + const float* data; + (void)*reinterpret_cast<const TARGETTYPE*>(data); // no warning +} + +template <int size> +void cast_nontype_template_true_positive_noninstantiated() { + const float *data; + const int arr[size]; + (void)*reinterpret_cast<const int*>(data); // expected-warning {{dereference of type 'const int *' that was reinterpret_cast from type 'const float *' has undefined behavior}} +} + +template <int size> +void cast_nontype_template_true_negative_noninstantiated() { + const int data[size]; + (void)*reinterpret_cast<const int*>(data); // no warning +} + +void top() { + cast_instantiated_badly<int, float>(); + // expected-note@-1 {{in instantiation of function template specialization 'templated::cast_instantiated_badly<int, float>' requested here}} + cast_instantiated_well<int, int>(); + cast_one_tmpl_arg_instantiated_badly<int>(); + // expected-note@-1 {{in instantiation of function template specialization 'templated::cast_one_tmpl_arg_instantiated_badly<int>' requested here}} + cast_one_tmpl_arg_instantiated_well<float>(); +} + +template<typename T, typename U> +void cast_template_dependent_type_noninstantiated(T** x) +{ + (void)*reinterpret_cast<U**>(x); +} + +template<typename T, typename U> +void cast_template_dependent_member_type_noninstantiated(typename T::X x) +{ + (void)*reinterpret_cast<typename U::Y>(x); +} + +} // namespace templated _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
