[Flang][OpenMP] crash on declare reduction directive

[k-arrows]

The first testcase:

function func()
!$omp declare reduction (foo : integer : omp_out = omp_out + omp_in)
end

Flang emits the error: not yet implemented: OpenMPDeclareReductionConstruct. This seems to indicate the feature is not yet implemented, which is expected behavior.

The second testcase:
https://godbolt.org/z/GEdsWsYY7

pure function func()
!$omp declare reduction (foo : integer : omp_out = omp_out + omp_in)
end

In this case, Flang crashes.

Backtrace:

flang-21: warning: OpenMP support in flang is still experimental [-Wexperimental-option]
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
Stack dump:
0.	Program arguments: /opt/compiler-explorer/clang-llvmflang-trunk-20250523/bin/flang -fc1 -triple x86_64-unknown-linux-gnu -S -mrelocation-model pic -pic-level 2 -pic-is-pie -target-cpu x86-64 -mllvm -x86-asm-syntax=intel -fopenmp -resource-dir /opt/compiler-explorer/clang-llvmflang-trunk-20250523/lib/clang/21 -mframe-pointer=all -o /app/output.s -x f95 /app/example.f90
 #0 0x0000000003e7dcd8 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/opt/compiler-explorer/clang-llvmflang-trunk-20250523/bin/flang+0x3e7dcd8)
 #1 0x0000000003e7b894 SignalHandler(int, siginfo_t*, void*) Signals.cpp:0:0
 #2 0x0000779d90242520 (/lib/x86_64-linux-gnu/libc.so.6+0x42520)
 #3 0x0000779d902969fc pthread_kill (/lib/x86_64-linux-gnu/libc.so.6+0x969fc)
 #4 0x0000779d90242476 gsignal (/lib/x86_64-linux-gnu/libc.so.6+0x42476)
 #5 0x0000779d902287f3 abort (/lib/x86_64-linux-gnu/libc.so.6+0x287f3)
 #6 0x000000000206f947 void Fortran::parser::detail::ParseTreeVisitorLookupScope::Walk<Fortran::parser::KindParam, Fortran::semantics::CanonicalizationOfAcc>(std::optional<Fortran::parser::KindParam>&, Fortran::semantics::CanonicalizationOfAcc&) (.isra.0.part.0.cold) canonicalize-acc.cpp:0:0
 #7 0x0000000004a3b0be Fortran::semantics::AssignmentContext::Analyze(Fortran::parser::AssignmentStmt const&) (/opt/compiler-explorer/clang-llvmflang-trunk-20250523/bin/flang+0x4a3b0be)
 #8 0x00000000049acdee std::enable_if<TupleTrait<Fortran::parser::AssignmentStmt>, void>::type Fortran::parser::detail::ParseTreeVisitorLookupScope::Walk<Fortran::parser::AssignmentStmt, Fortran::semantics::SemanticsVisitor<Fortran::semantics::AllocateChecker, Fortran::semantics::ArithmeticIfStmtChecker, Fortran::semantics::AssignmentChecker, Fortran::semantics::CaseChecker, Fortran::semantics::CoarrayChecker, Fortran::semantics::DataChecker, Fortran::semantics::DeallocateChecker, Fortran::semantics::DoForallChecker, Fortran::semantics::IfStmtChecker, Fortran::semantics::IoChecker, Fortran::semantics::MiscChecker, Fortran::semantics::NamelistChecker, Fortran::semantics::NullifyChecker, Fortran::semantics::PurityChecker, Fortran::semantics::ReturnStmtChecker, Fortran::semantics::SelectRankConstructChecker, Fortran::semantics::SelectTypeChecker, Fortran::semantics::StopChecker>>(Fortran::parser::AssignmentStmt const&, Fortran::semantics::SemanticsVisitor<Fortran::semantics::AllocateChecker, Fortran::semantics::ArithmeticIfStmtChecker, Fortran::semantics::AssignmentChecker, Fortran::semantics::CaseChecker, Fortran::semantics::CoarrayChecker, Fortran::semantics::DataChecker, Fortran::semantics::DeallocateChecker, Fortran::semantics::DoForallChecker, Fortran::semantics::IfStmtChecker, Fortran::semantics::IoChecker, Fortran::semantics::MiscChecker, Fortran::semantics::NamelistChecker, Fortran::semantics::NullifyChecker, Fortran::semantics::PurityChecker, Fortran::semantics::ReturnStmtChecker, Fortran::semantics::SelectRankConstructChecker, Fortran::semantics::SelectTypeChecker, Fortran::semantics::StopChecker>&) (/opt/compiler-explorer/clang-llvmflang-trunk-20250523/bin/flang+0x49acdee)
 #9 0x00000000049d6de3 void Fortran::parser::detail::ParseTreeVisitorLookupScope::ForEachInTuple<1ul, void Fortran::parser::detail::ParseTreeVisitorLookupScope::Walk<Fortran::semantics::SemanticsVisitor<Fortran::semantics::AllocateChecker, Fortran::semantics::ArithmeticIfStmtChecker, Fortran::semantics::AssignmentChecker, Fortran::semantics::CaseChecker, Fortran::semantics::CoarrayChecker, Fortran::semantics::DataChecker, Fortran::semantics::DeallocateChecker, Fortran::semantics::DoForallChecker, Fortran::semantics::IfStmtChecker, Fortran::semantics::IoChecker, Fortran::semantics::MiscChecker, Fortran::semantics::NamelistChecker, Fortran::semantics::NullifyChecker, Fortran::semantics::PurityChecker, Fortran::semantics::ReturnStmtChecker, Fortran::semantics::SelectRankConstructChecker, Fortran::semantics::SelectTypeChecker, Fortran::semantics::StopChecker>, std::__cxx11::list<Fortran::parser::OpenACCDeclarativeConstruct, std::allocator<Fortran::parser::OpenACCDeclarativeConstruct>>, std::__cxx11::list<Fortran::parser::OpenMPDeclarativeConstruct, std::allocator<Fortran::parser::OpenMPDeclarativeConstruct>>, std::__cxx11::list<Fortran::common::Indirection<Fortran::parser::CompilerDirective, false>, std::allocator<Fortran::common::Indirection<Fortran::parser::CompilerDirective, false>>>, std::__cxx11::list<Fortran::parser::Statement<Fortran::common::Indirection<Fortran::parser::UseStmt, false>>, std::allocator<Fortran::parser::Statement<Fortran::common::Indirection<Fortran::parser::UseStmt, false>>>>, std::__cxx11::list<Fortran::parser::Statement<Fortran::common::Indirection<Fortran::parser::ImportStmt, false>>, std::allocator<Fortran::parser::Statement<Fortran::common::Indirection<Fortran::parser::ImportStmt, false>>>>, Fortran::parser::ImplicitPart, std::__cxx11::list<Fortran::parser::DeclarationConstruct, std::allocator<Fortran::parser::DeclarationConstruct>>>(std::tuple<std::__cxx11::list<Fortran::parser::OpenACCDeclarativeConstruct, std::allocator<Fortran::parser::OpenACCDeclarativeConstruct>>, std::__cxx11::list<Fortran::parser::OpenMPDeclarativeConstruct, std::allocator<Fortran::parser::OpenMPDeclarativeConstruct>>, std::__cxx11::list<Fortran::common::Indirection<Fortran::parser::CompilerDirective, false>, std::allocator<Fortran::common::Indirection<Fortran::parser::CompilerDirective, false>>>, std::__cxx11::list<Fortran::parser::Statement<Fortran::common::Indirection<Fortran::parser::UseStmt, false>>, std::allocator<Fortran::parser::Statement<Fortran::common::Indirection<Fortran::parser::UseStmt, false>>>>, std::__cxx11::list<Fortran::parser::Statement<Fortran::common::Indirection<Fortran::parser::ImportStmt, false>>, std::allocator<Fortran::parser::Statement<Fortran::common::Indirection<Fortran::parser::ImportStmt, false>>>>, Fortran::parser::ImplicitPart, std::__cxx11::list<Fortran::parser::DeclarationConstruct, std::allocator<Fortran::parser::DeclarationConstruct>>> const&, Fortran::semantics::SemanticsVisitor<Fortran::semantics::AllocateChecker, Fortran::semantics::ArithmeticIfStmtChecker, Fortran::semantics::AssignmentChecker, Fortran::semantics::CaseChecker, Fortran::semantics::CoarrayChecker, Fortran::semantics::DataChecker, Fortran::semantics::DeallocateChecker, Fortran::semantics::DoForallChecker, Fortran::semantics::IfStmtChecker, Fortran::semantics::IoChecker, Fortran::semantics::MiscChecker, Fortran::semantics::NamelistChecker, Fortran::semantics::NullifyChecker, Fortran::semantics::PurityChecker, Fortran::semantics::ReturnStmtChecker, Fortran::semantics::SelectRankConstructChecker, Fortran::semantics::SelectTypeChecker, Fortran::semantics::StopChecker>&)::'lambda'(Fortran::semantics::SemanticsVisitor<Fortran::semantics::AllocateChecker, Fortran::semantics::ArithmeticIfStmtChecker, Fortran::semantics::AssignmentChecker, Fortran::semantics::CaseChecker, Fortran::semantics::CoarrayChecker, Fortran::semantics::DataChecker, Fortran::semantics::DeallocateChecker, Fortran::semantics::DoForallChecker, Fortran::semantics::IfStmtChecker, Fortran::semantics::IoChecker, Fortran::semantics::MiscChecker, Fortran::semantics::NamelistChecker, Fortran::semantics::NullifyChecker, Fortran::semantics::PurityChecker, Fortran::semantics::ReturnStmtChecker, Fortran::semantics::SelectRankConstructChecker, Fortran::semantics::SelectTypeChecker, Fortran::semantics::StopChecker> const&), std::tuple<std::__cxx11::list<Fortran::parser::OpenACCDeclarativeConstruct, std::allocator<Fortran::parser::OpenACCDeclarativeConstruct>>, std::__cxx11::list<Fortran::parser::OpenMPDeclarativeConstruct, std::allocator<Fortran::parser::OpenMPDeclarativeConstruct>>, std::__cxx11::list<Fortran::common::Indirection<Fortran::parser::CompilerDirective, false>, std::allocator<Fortran::common::Indirection<Fortran::parser::CompilerDirective, false>>>, std::__cxx11::list<Fortran::parser::Statement<Fortran::common::Indirection<Fortran::parser::UseStmt, false>>, std::allocator<Fortran::parser::Statement<Fortran::common::Indirection<Fortran::parser::UseStmt, false>>>>, std::__cxx11::list<Fortran::parser::Statement<Fortran::common::Indirection<Fortran::parser::ImportStmt, false>>, std::allocator<Fortran::parser::Statement<Fortran::common::Indirection<Fortran::parser::ImportStmt, false>>>>, Fortran::parser::ImplicitPart, std::__cxx11::list<Fortran::parser::DeclarationConstruct, std::allocator<Fortran::parser::DeclarationConstruct>>>>(std::tuple<std::__cxx11::list<Fortran::parser::OpenACCDeclarativeConstruct, std::allocator<Fortran::parser::OpenACCDeclarativeConstruct>>, std::__cxx11::list<Fortran::parser::OpenMPDeclarativeConstruct, std::allocator<Fortran::parser::OpenMPDeclarativeConstruct>>, std::__cxx11::list<Fortran::common::Indirection<Fortran::parser::CompilerDirective, false>, std::allocator<Fortran::common::Indirection<Fortran::parser::CompilerDirective, false>>>, std::__cxx11::list<Fortran::parser::Statement<Fortran::common::Indirection<Fortran::parser::UseStmt, false>>, std::allocator<Fortran::parser::Statement<Fortran::common::Indirection<Fortran::parser::UseStmt, false>>>>, std::__cxx11::list<Fortran::parser::Statement<Fortran::common::Indirection<Fortran::parser::ImportStmt, false>>, std::allocator<Fortran::parser::Statement<Fortran::common::Indirection<Fortran::parser::ImportStmt, false>>>>, Fortran::parser::ImplicitPart, std::__cxx11::list<Fortran::parser::DeclarationConstruct, std::allocator<Fortran::parser::DeclarationConstruct>>> const&, void Fortran::parser::detail::ParseTreeVisitorLookupScope::Walk<Fortran::semantics::SemanticsVisitor<Fortran::semantics::AllocateChecker, Fortran::semantics::ArithmeticIfStmtChecker, Fortran::semantics::AssignmentChecker, Fortran::semantics::CaseChecker, Fortran::semantics::CoarrayChecker, Fortran::semantics::DataChecker, Fortran::semantics::DeallocateChecker, Fortran::semantics::DoForallChecker, Fortran::semantics::IfStmtChecker, Fortran::semantics::IoChecker, Fortran::semantics::MiscChecker, Fortran::semantics::NamelistChecker, Fortran::semantics::NullifyChecker, Fortran::semantics::PurityChecker, Fortran::semantics::ReturnStmtChecker, Fortran::semantics::SelectRankConstructChecker, Fortran::semantics::SelectTypeChecker, Fortran::semantics::StopChecker>, std::__cxx11::list<Fortran::parser::OpenACCDeclarativeConstruct, std::allocator<Fortran::parser::OpenACCDeclarativeConstruct>>, std::__cxx11::list<Fortran::parser::OpenMPDeclarativeConstruct, std::allocator<Fortran::parser::OpenMPDeclarativeConstruct>>, std::__cxx11::list<Fortran::common::Indirection<Fortran::parser::CompilerDirective, false>, std::allocator<Fortran::common::Indirection<Fortran::parser::CompilerDirective, false>>>, std::__cxx11::list<Fortran::parser::Statement<Fortran::common::Indirection<Fortran::parser::UseStmt, false>>, std::allocator<Fortran::parser::Statement<Fortran::common::Indirection<Fortran::parser::UseStmt, false>>>>, std::__cxx11::list<Fortran::parser::Statement<Fortran::common::Indirection<Fortran::parser::ImportStmt, false>>, std::allocator<Fortran::parser::Statement<Fortran::common::Indirection<Fortran::parser::ImportStmt, false>>>>, Fortran::parser::ImplicitPart, std::__cxx11::list<Fortran::parser::DeclarationConstruct, std::allocator<Fortran::parser::DeclarationConstruct>>>(std::tuple<std::__cxx11::list<Fortran::parser::OpenACCDeclarativeConstruct, std::allocator<Fortran::parser::OpenACCDeclarativeConstruct>>, std::__cxx11::list<Fortran::parser::OpenMPDeclarativeConstruct, std::allocator<Fortran::parser::OpenMPDeclarativeConstruct>>, std::__cxx11::list<Fortran::common::Indirection<Fortran::parser::CompilerDirective, false>, std::allocator<Fortran::common::Indirection<Fortran::parser::CompilerDirective, false>>>, std::__cxx11::list<Fortran::parser::Statement<Fortran::common::Indirection<Fortran::parser::UseStmt, false>>, std::allocator<Fortran::parser::Statement<Fortran::common::Indirection<Fortran::parser::UseStmt, false>>>>, std::__cxx11::list<Fortran::parser::Statement<Fortran::common::Indirection<Fortran::parser::ImportStmt, false>>, std::allocator<Fortran::parser::Statement<Fortran::common::Indirection<Fortran::parser::ImportStmt, false>>>>, Fortran::parser::ImplicitPart, std::__cxx11::list<Fortran::parser::DeclarationConstruct, std::allocator<Fortran::parser::DeclarationConstruct>>> const&, Fortran::semantics::SemanticsVisitor<Fortran::semantics::AllocateChecker, Fortran::semantics::ArithmeticIfStmtChecker, Fortran::semantics::AssignmentChecker, Fortran::semantics::CaseChecker, Fortran::semantics::CoarrayChecker, Fortran::semantics::DataChecker, Fortran::semantics::DeallocateChecker, Fortran::semantics::DoForallChecker, Fortran::semantics::IfStmtChecker, Fortran::semantics::IoChecker, Fortran::semantics::MiscChecker, Fortran::semantics::NamelistChecker, Fortran::semantics::NullifyChecker, Fortran::semantics::PurityChecker, Fortran::semantics::ReturnStmtChecker, Fortran::semantics::SelectRankConstructChecker, Fortran::semantics::SelectTypeChecker, Fortran::semantics::StopChecker>&)::'lambda'(Fortran::semantics::SemanticsVisitor<Fortran::semantics::AllocateChecker, Fortran::semantics::ArithmeticIfStmtChecker, Fortran::semantics::AssignmentChecker, Fortran::semantics::CaseChecker, Fortran::semantics::CoarrayChecker, Fortran::semantics::DataChecker, Fortran::semantics::DeallocateChecker, Fortran::semantics::DoForallChecker, Fortran::semantics::IfStmtChecker, Fortran::semantics::IoChecker, Fortran::semantics::MiscChecker, Fortran::semantics::NamelistChecker, Fortran::semantics::NullifyChecker, Fortran::semantics::PurityChecker, Fortran::semantics::ReturnStmtChecker, Fortran::semantics::SelectRankConstructChecker, Fortran::semantics::SelectTypeChecker, Fortran::semantics::StopChecker> const&)) (/opt/compiler-explorer/clang-llvmflang-trunk-20250523/bin/flang+0x49d6de3)
#10 0x00000000049d9114 std::enable_if<TupleTrait<Fortran::parser::FunctionSubprogram>, void>::type Fortran::parser::detail::ParseTreeVisitorLookupScope::Walk<Fortran::parser::FunctionSubprogram, Fortran::semantics::SemanticsVisitor<Fortran::semantics::AllocateChecker, Fortran::semantics::ArithmeticIfStmtChecker, Fortran::semantics::AssignmentChecker, Fortran::semantics::CaseChecker, Fortran::semantics::CoarrayChecker, Fortran::semantics::DataChecker, Fortran::semantics::DeallocateChecker, Fortran::semantics::DoForallChecker, Fortran::semantics::IfStmtChecker, Fortran::semantics::IoChecker, Fortran::semantics::MiscChecker, Fortran::semantics::NamelistChecker, Fortran::semantics::NullifyChecker, Fortran::semantics::PurityChecker, Fortran::semantics::ReturnStmtChecker, Fortran::semantics::SelectRankConstructChecker, Fortran::semantics::SelectTypeChecker, Fortran::semantics::StopChecker>>(Fortran::parser::FunctionSubprogram const&, Fortran::semantics::SemanticsVisitor<Fortran::semantics::AllocateChecker, Fortran::semantics::ArithmeticIfStmtChecker, Fortran::semantics::AssignmentChecker, Fortran::semantics::CaseChecker, Fortran::semantics::CoarrayChecker, Fortran::semantics::DataChecker, Fortran::semantics::DeallocateChecker, Fortran::semantics::DoForallChecker, Fortran::semantics::IfStmtChecker, Fortran::semantics::IoChecker, Fortran::semantics::MiscChecker, Fortran::semantics::NamelistChecker, Fortran::semantics::NullifyChecker, Fortran::semantics::PurityChecker, Fortran::semantics::ReturnStmtChecker, Fortran::semantics::SelectRankConstructChecker, Fortran::semantics::SelectTypeChecker, Fortran::semantics::StopChecker>&) (/opt/compiler-explorer/clang-llvmflang-trunk-20250523/bin/flang+0x49d9114)
#11 0x00000000049d9845 void Fortran::common::log2visit::Log2VisitHelper<0ul, 7ul, void, void Fortran::parser::detail::ParseTreeVisitorLookupScope::Walk<Fortran::semantics::SemanticsVisitor<Fortran::semantics::AllocateChecker, Fortran::semantics::ArithmeticIfStmtChecker, Fortran::semantics::AssignmentChecker, Fortran::semantics::CaseChecker, Fortran::semantics::CoarrayChecker, Fortran::semantics::DataChecker, Fortran::semantics::DeallocateChecker, Fortran::semantics::DoForallChecker, Fortran::semantics::IfStmtChecker, Fortran::semantics::IoChecker, Fortran::semantics::MiscChecker, Fortran::semantics::NamelistChecker, Fortran::semantics::NullifyChecker, Fortran::semantics::PurityChecker, Fortran::semantics::ReturnStmtChecker, Fortran::semantics::SelectRankConstructChecker, Fortran::semantics::SelectTypeChecker, Fortran::semantics::StopChecker>, Fortran::common::Indirection<Fortran::parser::MainProgram, false>, Fortran::common::Indirection<Fortran::parser::FunctionSubprogram, false>, Fortran::common::Indirection<Fortran::parser::SubroutineSubprogram, false>, Fortran::common::Indirection<Fortran::parser::Module, false>, Fortran::common::Indirection<Fortran::parser::Submodule, false>, Fortran::common::Indirection<Fortran::parser::BlockData, false>, Fortran::common::Indirection<Fortran::parser::CompilerDirective, false>, Fortran::common::Indirection<Fortran::parser::OpenACCRoutineConstruct, false>>(std::variant<Fortran::common::Indirection<Fortran::parser::MainProgram, false>, Fortran::common::Indirection<Fortran::parser::FunctionSubprogram, false>, Fortran::common::Indirection<Fortran::parser::SubroutineSubprogram, false>, Fortran::common::Indirection<Fortran::parser::Module, false>, Fortran::common::Indirection<Fortran::parser::Submodule, false>, Fortran::common::Indirection<Fortran::parser::BlockData, false>, Fortran::common::Indirection<Fortran::parser::CompilerDirective, false>, Fortran::common::Indirection<Fortran::parser::OpenACCRoutineConstruct, false>> const&, Fortran::semantics::SemanticsVisitor<Fortran::semantics::AllocateChecker, Fortran::semantics::ArithmeticIfStmtChecker, Fortran::semantics::AssignmentChecker, Fortran::semantics::CaseChecker, Fortran::semantics::CoarrayChecker, Fortran::semantics::DataChecker, Fortran::semantics::DeallocateChecker, Fortran::semantics::DoForallChecker, Fortran::semantics::IfStmtChecker, Fortran::semantics::IoChecker, Fortran::semantics::MiscChecker, Fortran::semantics::NamelistChecker, Fortran::semantics::NullifyChecker, Fortran::semantics::PurityChecker, Fortran::semantics::ReturnStmtChecker, Fortran::semantics::SelectRankConstructChecker, Fortran::semantics::SelectTypeChecker, Fortran::semantics::StopChecker>&)::'lambda'(Fortran::semantics::SemanticsVisitor<Fortran::semantics::AllocateChecker, Fortran::semantics::ArithmeticIfStmtChecker, Fortran::semantics::AssignmentChecker, Fortran::semantics::CaseChecker, Fortran::semantics::CoarrayChecker, Fortran::semantics::DataChecker, Fortran::semantics::DeallocateChecker, Fortran::semantics::DoForallChecker, Fortran::semantics::IfStmtChecker, Fortran::semantics::IoChecker, Fortran::semantics::MiscChecker, Fortran::semantics::NamelistChecker, Fortran::semantics::NullifyChecker, Fortran::semantics::PurityChecker, Fortran::semantics::ReturnStmtChecker, Fortran::semantics::SelectRankConstructChecker, Fortran::semantics::SelectTypeChecker, Fortran::semantics::StopChecker> const&), std::variant<Fortran::common::Indirection<Fortran::parser::MainProgram, false>, Fortran::common::Indirection<Fortran::parser::FunctionSubprogram, false>, Fortran::common::Indirection<Fortran::parser::SubroutineSubprogram, false>, Fortran::common::Indirection<Fortran::parser::Module, false>, Fortran::common::Indirection<Fortran::parser::Submodule, false>, Fortran::common::Indirection<Fortran::parser::BlockData, false>, Fortran::common::Indirection<Fortran::parser::CompilerDirective, false>, Fortran::common::Indirection<Fortran::parser::OpenACCRoutineConstruct, false>> const&>(void Fortran::parser::detail::ParseTreeVisitorLookupScope::Walk<Fortran::semantics::SemanticsVisitor<Fortran::semantics::AllocateChecker, Fortran::semantics::ArithmeticIfStmtChecker, Fortran::semantics::AssignmentChecker, Fortran::semantics::CaseChecker, Fortran::semantics::CoarrayChecker, Fortran::semantics::DataChecker, Fortran::semantics::DeallocateChecker, Fortran::semantics::DoForallChecker, Fortran::semantics::IfStmtChecker, Fortran::semantics::IoChecker, Fortran::semantics::MiscChecker, Fortran::semantics::NamelistChecker, Fortran::semantics::NullifyChecker, Fortran::semantics::PurityChecker, Fortran::semantics::ReturnStmtChecker, Fortran::semantics::SelectRankConstructChecker, Fortran::semantics::SelectTypeChecker, Fortran::semantics::StopChecker>, Fortran::common::Indirection<Fortran::parser::MainProgram, false>, Fortran::common::Indirection<Fortran::parser::FunctionSubprogram, false>, Fortran::common::Indirection<Fortran::parser::SubroutineSubprogram, false>, Fortran::common::Indirection<Fortran::parser::Module, false>, Fortran::common::Indirection<Fortran::parser::Submodule, false>, Fortran::common::Indirection<Fortran::parser::BlockData, false>, Fortran::common::Indirection<Fortran::parser::CompilerDirective, false>, Fortran::common::Indirection<Fortran::parser::OpenACCRoutineConstruct, false>>(std::variant<Fortran::common::Indirection<Fortran::parser::MainProgram, false>, Fortran::common::Indirection<Fortran::parser::FunctionSubprogram, false>, Fortran::common::Indirection<Fortran::parser::SubroutineSubprogram, false>, Fortran::common::Indirection<Fortran::parser::Module, false>, Fortran::common::Indirection<Fortran::parser::Submodule, false>, Fortran::common::Indirection<Fortran::parser::BlockData, false>, Fortran::common::Indirection<Fortran::parser::CompilerDirective, false>, Fortran::common::Indirection<Fortran::parser::OpenACCRoutineConstruct, false>> const&, Fortran::semantics::SemanticsVisitor<Fortran::semantics::AllocateChecker, Fortran::semantics::ArithmeticIfStmtChecker, Fortran::semantics::AssignmentChecker, Fortran::semantics::CaseChecker, Fortran::semantics::CoarrayChecker, Fortran::semantics::DataChecker, Fortran::semantics::DeallocateChecker, Fortran::semantics::DoForallChecker, Fortran::semantics::IfStmtChecker, Fortran::semantics::IoChecker, Fortran::semantics::MiscChecker, Fortran::semantics::NamelistChecker, Fortran::semantics::NullifyChecker, Fortran::semantics::PurityChecker, Fortran::semantics::ReturnStmtChecker, Fortran::semantics::SelectRankConstructChecker, Fortran::semantics::SelectTypeChecker, Fortran::semantics::StopChecker>&)::'lambda'(Fortran::semantics::SemanticsVisitor<Fortran::semantics::AllocateChecker, Fortran::semantics::ArithmeticIfStmtChecker, Fortran::semantics::AssignmentChecker, Fortran::semantics::CaseChecker, Fortran::semantics::CoarrayChecker, Fortran::semantics::DataChecker, Fortran::semantics::DeallocateChecker, Fortran::semantics::DoForallChecker, Fortran::semantics::IfStmtChecker, Fortran::semantics::IoChecker, Fortran::semantics::MiscChecker, Fortran::semantics::NamelistChecker, Fortran::semantics::NullifyChecker, Fortran::semantics::PurityChecker, Fortran::semantics::ReturnStmtChecker, Fortran::semantics::SelectRankConstructChecker, Fortran::semantics::SelectTypeChecker, Fortran::semantics::StopChecker> const&)&&, unsigned long, std::variant<Fortran::common::Indirection<Fortran::parser::MainProgram, false>, Fortran::common::Indirection<Fortran::parser::FunctionSubprogram, false>, Fortran::common::Indirection<Fortran::parser::SubroutineSubprogram, false>, Fortran::common::Indirection<Fortran::parser::Module, false>, Fortran::common::Indirection<Fortran::parser::Submodule, false>, Fortran::common::Indirection<Fortran::parser::BlockData, false>, Fortran::common::Indirection<Fortran::parser::CompilerDirective, false>, Fortran::common::Indirection<Fortran::parser::OpenACCRoutineConstruct, false>> const&) (/opt/compiler-explorer/clang-llvmflang-trunk-20250523/bin/flang+0x49d9845)
#12 0x00000000049f38d8 Fortran::semantics::Semantics::Perform() (/opt/compiler-explorer/clang-llvmflang-trunk-20250523/bin/flang+0x49f38d8)
#13 0x0000000003ed6588 Fortran::frontend::FrontendAction::runSemanticChecks() (/opt/compiler-explorer/clang-llvmflang-trunk-20250523/bin/flang+0x3ed6588)
#14 0x0000000004188250 Fortran::frontend::CodeGenAction::beginSourceFileAction() (/opt/compiler-explorer/clang-llvmflang-trunk-20250523/bin/flang+0x4188250)
#15 0x0000000003ed51c5 Fortran::frontend::FrontendAction::beginSourceFile(Fortran::frontend::CompilerInstance&, Fortran::frontend::FrontendInputFile const&) (/opt/compiler-explorer/clang-llvmflang-trunk-20250523/bin/flang+0x3ed51c5)
#16 0x0000000003ec3cc7 Fortran::frontend::CompilerInstance::executeAction(Fortran::frontend::FrontendAction&) (/opt/compiler-explorer/clang-llvmflang-trunk-20250523/bin/flang+0x3ec3cc7)
#17 0x0000000003edeb33 Fortran::frontend::executeCompilerInvocation(Fortran::frontend::CompilerInstance*) (/opt/compiler-explorer/clang-llvmflang-trunk-20250523/bin/flang+0x3edeb33)
#18 0x00000000021ef16a fc1_main(llvm::ArrayRef<char const*>, char const*) (/opt/compiler-explorer/clang-llvmflang-trunk-20250523/bin/flang+0x21ef16a)
#19 0x00000000020a5fff main (/opt/compiler-explorer/clang-llvmflang-trunk-20250523/bin/flang+0x20a5fff)
#20 0x0000779d90229d90 (/lib/x86_64-linux-gnu/libc.so.6+0x29d90)
#21 0x0000779d90229e40 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x29e40)
#22 0x00000000021edb35 _start (/opt/compiler-explorer/clang-llvmflang-trunk-20250523/bin/flang+0x21edb35)
flang-21: error: unable to execute command: Aborted (core dumped)
flang-21: error: flang frontend command failed due to signal (use -v to see invocation)
flang version 21.0.0git (https://github.com/llvm/llvm-project.git d6596482ef277269dd35b5ea0c0439173cba7636)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /opt/compiler-explorer/clang-llvmflang-trunk-20250523/bin
flang-21: warning: OpenMP support in flang is still experimental [-Wexperimental-option]
flang-21: note: diagnostic msg: 
********************

PLEASE ATTACH THE FOLLOWING FILES TO THE BUG REPORT:
Preprocessed source(s) and associated run script(s) are located at:
flang-21: note: diagnostic msg: /tmp/example-20d2b4
flang-21: note: diagnostic msg: /tmp/example-20d2b4.sh
flang-21: note: diagnostic msg: 

********************
Compiler returned: 254

[llvmbot]

@llvm/issue-subscribers-flang-frontend

Author: None (k-arrows)

The first testcase: ```f90 function func() !$omp declare reduction (foo : integer : omp_out = omp_out + omp_in) end ```

Flang emits the error: not yet implemented: OpenMPDeclareReductionConstruct. This seems to indicate the feature is not yet implemented, which is expected behavior.

The second testcase:
https://godbolt.org/z/GEdsWsYY7

pure function func()
!$omp declare reduction (foo : integer : omp_out = omp_out + omp_in)
end

In this case, Flang crashes.

Backtrace:

flang-21: warning: OpenMP support in flang is still experimental [-Wexperimental-option]
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
Stack dump:
0.	Program arguments: /opt/compiler-explorer/clang-llvmflang-trunk-20250523/bin/flang -fc1 -triple x86_64-unknown-linux-gnu -S -mrelocation-model pic -pic-level 2 -pic-is-pie -target-cpu x86-64 -mllvm -x86-asm-syntax=intel -fopenmp -resource-dir /opt/compiler-explorer/clang-llvmflang-trunk-20250523/lib/clang/21 -mframe-pointer=all -o /app/output.s -x f95 /app/example.f90
 #<!-- -->0 0x0000000003e7dcd8 llvm::sys::PrintStackTrace(llvm::raw_ostream&amp;, int) (/opt/compiler-explorer/clang-llvmflang-trunk-20250523/bin/flang+0x3e7dcd8)
 #<!-- -->1 0x0000000003e7b894 SignalHandler(int, siginfo_t*, void*) Signals.cpp:0:0
 #<!-- -->2 0x0000779d90242520 (/lib/x86_64-linux-gnu/libc.so.6+0x42520)
 #<!-- -->3 0x0000779d902969fc pthread_kill (/lib/x86_64-linux-gnu/libc.so.6+0x969fc)
 #<!-- -->4 0x0000779d90242476 gsignal (/lib/x86_64-linux-gnu/libc.so.6+0x42476)
 #<!-- -->5 0x0000779d902287f3 abort (/lib/x86_64-linux-gnu/libc.so.6+0x287f3)
 #<!-- -->6 0x000000000206f947 void Fortran::parser::detail::ParseTreeVisitorLookupScope::Walk&lt;Fortran::parser::KindParam, Fortran::semantics::CanonicalizationOfAcc&gt;(std::optional&lt;Fortran::parser::KindParam&gt;&amp;, Fortran::semantics::CanonicalizationOfAcc&amp;) (.isra.0.part.0.cold) canonicalize-acc.cpp:0:0
 #<!-- -->7 0x0000000004a3b0be Fortran::semantics::AssignmentContext::Analyze(Fortran::parser::AssignmentStmt const&amp;) (/opt/compiler-explorer/clang-llvmflang-trunk-20250523/bin/flang+0x4a3b0be)
 #<!-- -->8 0x00000000049acdee std::enable_if&lt;TupleTrait&lt;Fortran::parser::AssignmentStmt&gt;, void&gt;::type Fortran::parser::detail::ParseTreeVisitorLookupScope::Walk&lt;Fortran::parser::AssignmentStmt, Fortran::semantics::SemanticsVisitor&lt;Fortran::semantics::AllocateChecker, Fortran::semantics::ArithmeticIfStmtChecker, Fortran::semantics::AssignmentChecker, Fortran::semantics::CaseChecker, Fortran::semantics::CoarrayChecker, Fortran::semantics::DataChecker, Fortran::semantics::DeallocateChecker, Fortran::semantics::DoForallChecker, Fortran::semantics::IfStmtChecker, Fortran::semantics::IoChecker, Fortran::semantics::MiscChecker, Fortran::semantics::NamelistChecker, Fortran::semantics::NullifyChecker, Fortran::semantics::PurityChecker, Fortran::semantics::ReturnStmtChecker, Fortran::semantics::SelectRankConstructChecker, Fortran::semantics::SelectTypeChecker, Fortran::semantics::StopChecker&gt;&gt;(Fortran::parser::AssignmentStmt const&amp;, Fortran::semantics::SemanticsVisitor&lt;Fortran::semantics::AllocateChecker, Fortran::semantics::ArithmeticIfStmtChecker, Fortran::semantics::AssignmentChecker, Fortran::semantics::CaseChecker, Fortran::semantics::CoarrayChecker, Fortran::semantics::DataChecker, Fortran::semantics::DeallocateChecker, Fortran::semantics::DoForallChecker, Fortran::semantics::IfStmtChecker, Fortran::semantics::IoChecker, Fortran::semantics::MiscChecker, Fortran::semantics::NamelistChecker, Fortran::semantics::NullifyChecker, Fortran::semantics::PurityChecker, Fortran::semantics::ReturnStmtChecker, Fortran::semantics::SelectRankConstructChecker, Fortran::semantics::SelectTypeChecker, Fortran::semantics::StopChecker&gt;&amp;) (/opt/compiler-explorer/clang-llvmflang-trunk-20250523/bin/flang+0x49acdee)
 #<!-- -->9 0x00000000049d6de3 void Fortran::parser::detail::ParseTreeVisitorLookupScope::ForEachInTuple&lt;1ul, void Fortran::parser::detail::ParseTreeVisitorLookupScope::Walk&lt;Fortran::semantics::SemanticsVisitor&lt;Fortran::semantics::AllocateChecker, Fortran::semantics::ArithmeticIfStmtChecker, Fortran::semantics::AssignmentChecker, Fortran::semantics::CaseChecker, Fortran::semantics::CoarrayChecker, Fortran::semantics::DataChecker, Fortran::semantics::DeallocateChecker, Fortran::semantics::DoForallChecker, Fortran::semantics::IfStmtChecker, Fortran::semantics::IoChecker, Fortran::semantics::MiscChecker, Fortran::semantics::NamelistChecker, Fortran::semantics::NullifyChecker, Fortran::semantics::PurityChecker, Fortran::semantics::ReturnStmtChecker, Fortran::semantics::SelectRankConstructChecker, Fortran::semantics::SelectTypeChecker, Fortran::semantics::StopChecker&gt;, std::__cxx11::list&lt;Fortran::parser::OpenACCDeclarativeConstruct, std::allocator&lt;Fortran::parser::OpenACCDeclarativeConstruct&gt;&gt;, std::__cxx11::list&lt;Fortran::parser::OpenMPDeclarativeConstruct, std::allocator&lt;Fortran::parser::OpenMPDeclarativeConstruct&gt;&gt;, std::__cxx11::list&lt;Fortran::common::Indirection&lt;Fortran::parser::CompilerDirective, false&gt;, std::allocator&lt;Fortran::common::Indirection&lt;Fortran::parser::CompilerDirective, false&gt;&gt;&gt;, std::__cxx11::list&lt;Fortran::parser::Statement&lt;Fortran::common::Indirection&lt;Fortran::parser::UseStmt, false&gt;&gt;, std::allocator&lt;Fortran::parser::Statement&lt;Fortran::common::Indirection&lt;Fortran::parser::UseStmt, false&gt;&gt;&gt;&gt;, std::__cxx11::list&lt;Fortran::parser::Statement&lt;Fortran::common::Indirection&lt;Fortran::parser::ImportStmt, false&gt;&gt;, std::allocator&lt;Fortran::parser::Statement&lt;Fortran::common::Indirection&lt;Fortran::parser::ImportStmt, false&gt;&gt;&gt;&gt;, Fortran::parser::ImplicitPart, std::__cxx11::list&lt;Fortran::parser::DeclarationConstruct, std::allocator&lt;Fortran::parser::DeclarationConstruct&gt;&gt;&gt;(std::tuple&lt;std::__cxx11::list&lt;Fortran::parser::OpenACCDeclarativeConstruct, std::allocator&lt;Fortran::parser::OpenACCDeclarativeConstruct&gt;&gt;, std::__cxx11::list&lt;Fortran::parser::OpenMPDeclarativeConstruct, std::allocator&lt;Fortran::parser::OpenMPDeclarativeConstruct&gt;&gt;, std::__cxx11::list&lt;Fortran::common::Indirection&lt;Fortran::parser::CompilerDirective, false&gt;, std::allocator&lt;Fortran::common::Indirection&lt;Fortran::parser::CompilerDirective, false&gt;&gt;&gt;, std::__cxx11::list&lt;Fortran::parser::Statement&lt;Fortran::common::Indirection&lt;Fortran::parser::UseStmt, false&gt;&gt;, std::allocator&lt;Fortran::parser::Statement&lt;Fortran::common::Indirection&lt;Fortran::parser::UseStmt, false&gt;&gt;&gt;&gt;, std::__cxx11::list&lt;Fortran::parser::Statement&lt;Fortran::common::Indirection&lt;Fortran::parser::ImportStmt, false&gt;&gt;, std::allocator&lt;Fortran::parser::Statement&lt;Fortran::common::Indirection&lt;Fortran::parser::ImportStmt, false&gt;&gt;&gt;&gt;, Fortran::parser::ImplicitPart, std::__cxx11::list&lt;Fortran::parser::DeclarationConstruct, std::allocator&lt;Fortran::parser::DeclarationConstruct&gt;&gt;&gt; const&amp;, Fortran::semantics::SemanticsVisitor&lt;Fortran::semantics::AllocateChecker, Fortran::semantics::ArithmeticIfStmtChecker, Fortran::semantics::AssignmentChecker, Fortran::semantics::CaseChecker, Fortran::semantics::CoarrayChecker, Fortran::semantics::DataChecker, Fortran::semantics::DeallocateChecker, Fortran::semantics::DoForallChecker, Fortran::semantics::IfStmtChecker, Fortran::semantics::IoChecker, Fortran::semantics::MiscChecker, Fortran::semantics::NamelistChecker, Fortran::semantics::NullifyChecker, Fortran::semantics::PurityChecker, Fortran::semantics::ReturnStmtChecker, Fortran::semantics::SelectRankConstructChecker, Fortran::semantics::SelectTypeChecker, Fortran::semantics::StopChecker&gt;&amp;)::'lambda'(Fortran::semantics::SemanticsVisitor&lt;Fortran::semantics::AllocateChecker, Fortran::semantics::ArithmeticIfStmtChecker, Fortran::semantics::AssignmentChecker, Fortran::semantics::CaseChecker, Fortran::semantics::CoarrayChecker, Fortran::semantics::DataChecker, Fortran::semantics::DeallocateChecker, Fortran::semantics::DoForallChecker, Fortran::semantics::IfStmtChecker, Fortran::semantics::IoChecker, Fortran::semantics::MiscChecker, Fortran::semantics::NamelistChecker, Fortran::semantics::NullifyChecker, Fortran::semantics::PurityChecker, Fortran::semantics::ReturnStmtChecker, Fortran::semantics::SelectRankConstructChecker, Fortran::semantics::SelectTypeChecker, Fortran::semantics::StopChecker&gt; const&amp;), std::tuple&lt;std::__cxx11::list&lt;Fortran::parser::OpenACCDeclarativeConstruct, std::allocator&lt;Fortran::parser::OpenACCDeclarativeConstruct&gt;&gt;, std::__cxx11::list&lt;Fortran::parser::OpenMPDeclarativeConstruct, std::allocator&lt;Fortran::parser::OpenMPDeclarativeConstruct&gt;&gt;, std::__cxx11::list&lt;Fortran::common::Indirection&lt;Fortran::parser::CompilerDirective, false&gt;, std::allocator&lt;Fortran::common::Indirection&lt;Fortran::parser::CompilerDirective, false&gt;&gt;&gt;, std::__cxx11::list&lt;Fortran::parser::Statement&lt;Fortran::common::Indirection&lt;Fortran::parser::UseStmt, false&gt;&gt;, std::allocator&lt;Fortran::parser::Statement&lt;Fortran::common::Indirection&lt;Fortran::parser::UseStmt, false&gt;&gt;&gt;&gt;, std::__cxx11::list&lt;Fortran::parser::Statement&lt;Fortran::common::Indirection&lt;Fortran::parser::ImportStmt, false&gt;&gt;, std::allocator&lt;Fortran::parser::Statement&lt;Fortran::common::Indirection&lt;Fortran::parser::ImportStmt, false&gt;&gt;&gt;&gt;, Fortran::parser::ImplicitPart, std::__cxx11::list&lt;Fortran::parser::DeclarationConstruct, std::allocator&lt;Fortran::parser::DeclarationConstruct&gt;&gt;&gt;&gt;(std::tuple&lt;std::__cxx11::list&lt;Fortran::parser::OpenACCDeclarativeConstruct, std::allocator&lt;Fortran::parser::OpenACCDeclarativeConstruct&gt;&gt;, std::__cxx11::list&lt;Fortran::parser::OpenMPDeclarativeConstruct, std::allocator&lt;Fortran::parser::OpenMPDeclarativeConstruct&gt;&gt;, std::__cxx11::list&lt;Fortran::common::Indirection&lt;Fortran::parser::CompilerDirective, false&gt;, std::allocator&lt;Fortran::common::Indirection&lt;Fortran::parser::CompilerDirective, false&gt;&gt;&gt;, std::__cxx11::list&lt;Fortran::parser::Statement&lt;Fortran::common::Indirection&lt;Fortran::parser::UseStmt, false&gt;&gt;, std::allocator&lt;Fortran::parser::Statement&lt;Fortran::common::Indirection&lt;Fortran::parser::UseStmt, false&gt;&gt;&gt;&gt;, std::__cxx11::list&lt;Fortran::parser::Statement&lt;Fortran::common::Indirection&lt;Fortran::parser::ImportStmt, false&gt;&gt;, std::allocator&lt;Fortran::parser::Statement&lt;Fortran::common::Indirection&lt;Fortran::parser::ImportStmt, false&gt;&gt;&gt;&gt;, Fortran::parser::ImplicitPart, std::__cxx11::list&lt;Fortran::parser::DeclarationConstruct, std::allocator&lt;Fortran::parser::DeclarationConstruct&gt;&gt;&gt; const&amp;, void Fortran::parser::detail::ParseTreeVisitorLookupScope::Walk&lt;Fortran::semantics::SemanticsVisitor&lt;Fortran::semantics::AllocateChecker, Fortran::semantics::ArithmeticIfStmtChecker, Fortran::semantics::AssignmentChecker, Fortran::semantics::CaseChecker, Fortran::semantics::CoarrayChecker, Fortran::semantics::DataChecker, Fortran::semantics::DeallocateChecker, Fortran::semantics::DoForallChecker, Fortran::semantics::IfStmtChecker, Fortran::semantics::IoChecker, Fortran::semantics::MiscChecker, Fortran::semantics::NamelistChecker, Fortran::semantics::NullifyChecker, Fortran::semantics::PurityChecker, Fortran::semantics::ReturnStmtChecker, Fortran::semantics::SelectRankConstructChecker, Fortran::semantics::SelectTypeChecker, Fortran::semantics::StopChecker&gt;, std::__cxx11::list&lt;Fortran::parser::OpenACCDeclarativeConstruct, std::allocator&lt;Fortran::parser::OpenACCDeclarativeConstruct&gt;&gt;, std::__cxx11::list&lt;Fortran::parser::OpenMPDeclarativeConstruct, std::allocator&lt;Fortran::parser::OpenMPDeclarativeConstruct&gt;&gt;, std::__cxx11::list&lt;Fortran::common::Indirection&lt;Fortran::parser::CompilerDirective, false&gt;, std::allocator&lt;Fortran::common::Indirection&lt;Fortran::parser::CompilerDirective, false&gt;&gt;&gt;, std::__cxx11::list&lt;Fortran::parser::Statement&lt;Fortran::common::Indirection&lt;Fortran::parser::UseStmt, false&gt;&gt;, std::allocator&lt;Fortran::parser::Statement&lt;Fortran::common::Indirection&lt;Fortran::parser::UseStmt, false&gt;&gt;&gt;&gt;, std::__cxx11::list&lt;Fortran::parser::Statement&lt;Fortran::common::Indirection&lt;Fortran::parser::ImportStmt, false&gt;&gt;, std::allocator&lt;Fortran::parser::Statement&lt;Fortran::common::Indirection&lt;Fortran::parser::ImportStmt, false&gt;&gt;&gt;&gt;, Fortran::parser::ImplicitPart, std::__cxx11::list&lt;Fortran::parser::DeclarationConstruct, std::allocator&lt;Fortran::parser::DeclarationConstruct&gt;&gt;&gt;(std::tuple&lt;std::__cxx11::list&lt;Fortran::parser::OpenACCDeclarativeConstruct, std::allocator&lt;Fortran::parser::OpenACCDeclarativeConstruct&gt;&gt;, std::__cxx11::list&lt;Fortran::parser::OpenMPDeclarativeConstruct, std::allocator&lt;Fortran::parser::OpenMPDeclarativeConstruct&gt;&gt;, std::__cxx11::list&lt;Fortran::common::Indirection&lt;Fortran::parser::CompilerDirective, false&gt;, std::allocator&lt;Fortran::common::Indirection&lt;Fortran::parser::CompilerDirective, false&gt;&gt;&gt;, std::__cxx11::list&lt;Fortran::parser::Statement&lt;Fortran::common::Indirection&lt;Fortran::parser::UseStmt, false&gt;&gt;, std::allocator&lt;Fortran::parser::Statement&lt;Fortran::common::Indirection&lt;Fortran::parser::UseStmt, false&gt;&gt;&gt;&gt;, std::__cxx11::list&lt;Fortran::parser::Statement&lt;Fortran::common::Indirection&lt;Fortran::parser::ImportStmt, false&gt;&gt;, std::allocator&lt;Fortran::parser::Statement&lt;Fortran::common::Indirection&lt;Fortran::parser::ImportStmt, false&gt;&gt;&gt;&gt;, Fortran::parser::ImplicitPart, std::__cxx11::list&lt;Fortran::parser::DeclarationConstruct, std::allocator&lt;Fortran::parser::DeclarationConstruct&gt;&gt;&gt; const&amp;, Fortran::semantics::SemanticsVisitor&lt;Fortran::semantics::AllocateChecker, Fortran::semantics::ArithmeticIfStmtChecker, Fortran::semantics::AssignmentChecker, Fortran::semantics::CaseChecker, Fortran::semantics::CoarrayChecker, Fortran::semantics::DataChecker, Fortran::semantics::DeallocateChecker, Fortran::semantics::DoForallChecker, Fortran::semantics::IfStmtChecker, Fortran::semantics::IoChecker, Fortran::semantics::MiscChecker, Fortran::semantics::NamelistChecker, Fortran::semantics::NullifyChecker, Fortran::semantics::PurityChecker, Fortran::semantics::ReturnStmtChecker, Fortran::semantics::SelectRankConstructChecker, Fortran::semantics::SelectTypeChecker, Fortran::semantics::StopChecker&gt;&amp;)::'lambda'(Fortran::semantics::SemanticsVisitor&lt;Fortran::semantics::AllocateChecker, Fortran::semantics::ArithmeticIfStmtChecker, Fortran::semantics::AssignmentChecker, Fortran::semantics::CaseChecker, Fortran::semantics::CoarrayChecker, Fortran::semantics::DataChecker, Fortran::semantics::DeallocateChecker, Fortran::semantics::DoForallChecker, Fortran::semantics::IfStmtChecker, Fortran::semantics::IoChecker, Fortran::semantics::MiscChecker, Fortran::semantics::NamelistChecker, Fortran::semantics::NullifyChecker, Fortran::semantics::PurityChecker, Fortran::semantics::ReturnStmtChecker, Fortran::semantics::SelectRankConstructChecker, Fortran::semantics::SelectTypeChecker, Fortran::semantics::StopChecker&gt; const&amp;)) (/opt/compiler-explorer/clang-llvmflang-trunk-20250523/bin/flang+0x49d6de3)
#<!-- -->10 0x00000000049d9114 std::enable_if&lt;TupleTrait&lt;Fortran::parser::FunctionSubprogram&gt;, void&gt;::type Fortran::parser::detail::ParseTreeVisitorLookupScope::Walk&lt;Fortran::parser::FunctionSubprogram, Fortran::semantics::SemanticsVisitor&lt;Fortran::semantics::AllocateChecker, Fortran::semantics::ArithmeticIfStmtChecker, Fortran::semantics::AssignmentChecker, Fortran::semantics::CaseChecker, Fortran::semantics::CoarrayChecker, Fortran::semantics::DataChecker, Fortran::semantics::DeallocateChecker, Fortran::semantics::DoForallChecker, Fortran::semantics::IfStmtChecker, Fortran::semantics::IoChecker, Fortran::semantics::MiscChecker, Fortran::semantics::NamelistChecker, Fortran::semantics::NullifyChecker, Fortran::semantics::PurityChecker, Fortran::semantics::ReturnStmtChecker, Fortran::semantics::SelectRankConstructChecker, Fortran::semantics::SelectTypeChecker, Fortran::semantics::StopChecker&gt;&gt;(Fortran::parser::FunctionSubprogram const&amp;, Fortran::semantics::SemanticsVisitor&lt;Fortran::semantics::AllocateChecker, Fortran::semantics::ArithmeticIfStmtChecker, Fortran::semantics::AssignmentChecker, Fortran::semantics::CaseChecker, Fortran::semantics::CoarrayChecker, Fortran::semantics::DataChecker, Fortran::semantics::DeallocateChecker, Fortran::semantics::DoForallChecker, Fortran::semantics::IfStmtChecker, Fortran::semantics::IoChecker, Fortran::semantics::MiscChecker, Fortran::semantics::NamelistChecker, Fortran::semantics::NullifyChecker, Fortran::semantics::PurityChecker, Fortran::semantics::ReturnStmtChecker, Fortran::semantics::SelectRankConstructChecker, Fortran::semantics::SelectTypeChecker, Fortran::semantics::StopChecker&gt;&amp;) (/opt/compiler-explorer/clang-llvmflang-trunk-20250523/bin/flang+0x49d9114)
#<!-- -->11 0x00000000049d9845 void Fortran::common::log2visit::Log2VisitHelper&lt;0ul, 7ul, void, void Fortran::parser::detail::ParseTreeVisitorLookupScope::Walk&lt;Fortran::semantics::SemanticsVisitor&lt;Fortran::semantics::AllocateChecker, Fortran::semantics::ArithmeticIfStmtChecker, Fortran::semantics::AssignmentChecker, Fortran::semantics::CaseChecker, Fortran::semantics::CoarrayChecker, Fortran::semantics::DataChecker, Fortran::semantics::DeallocateChecker, Fortran::semantics::DoForallChecker, Fortran::semantics::IfStmtChecker, Fortran::semantics::IoChecker, Fortran::semantics::MiscChecker, Fortran::semantics::NamelistChecker, Fortran::semantics::NullifyChecker, Fortran::semantics::PurityChecker, Fortran::semantics::ReturnStmtChecker, Fortran::semantics::SelectRankConstructChecker, Fortran::semantics::SelectTypeChecker, Fortran::semantics::StopChecker&gt;, Fortran::common::Indirection&lt;Fortran::parser::MainProgram, false&gt;, Fortran::common::Indirection&lt;Fortran::parser::FunctionSubprogram, false&gt;, Fortran::common::Indirection&lt;Fortran::parser::SubroutineSubprogram, false&gt;, Fortran::common::Indirection&lt;Fortran::parser::Module, false&gt;, Fortran::common::Indirection&lt;Fortran::parser::Submodule, false&gt;, Fortran::common::Indirection&lt;Fortran::parser::BlockData, false&gt;, Fortran::common::Indirection&lt;Fortran::parser::CompilerDirective, false&gt;, Fortran::common::Indirection&lt;Fortran::parser::OpenACCRoutineConstruct, false&gt;&gt;(std::variant&lt;Fortran::common::Indirection&lt;Fortran::parser::MainProgram, false&gt;, Fortran::common::Indirection&lt;Fortran::parser::FunctionSubprogram, false&gt;, Fortran::common::Indirection&lt;Fortran::parser::SubroutineSubprogram, false&gt;, Fortran::common::Indirection&lt;Fortran::parser::Module, false&gt;, Fortran::common::Indirection&lt;Fortran::parser::Submodule, false&gt;, Fortran::common::Indirection&lt;Fortran::parser::BlockData, false&gt;, Fortran::common::Indirection&lt;Fortran::parser::CompilerDirective, false&gt;, Fortran::common::Indirection&lt;Fortran::parser::OpenACCRoutineConstruct, false&gt;&gt; const&amp;, Fortran::semantics::SemanticsVisitor&lt;Fortran::semantics::AllocateChecker, Fortran::semantics::ArithmeticIfStmtChecker, Fortran::semantics::AssignmentChecker, Fortran::semantics::CaseChecker, Fortran::semantics::CoarrayChecker, Fortran::semantics::DataChecker, Fortran::semantics::DeallocateChecker, Fortran::semantics::DoForallChecker, Fortran::semantics::IfStmtChecker, Fortran::semantics::IoChecker, Fortran::semantics::MiscChecker, Fortran::semantics::NamelistChecker, Fortran::semantics::NullifyChecker, Fortran::semantics::PurityChecker, Fortran::semantics::ReturnStmtChecker, Fortran::semantics::SelectRankConstructChecker, Fortran::semantics::SelectTypeChecker, Fortran::semantics::StopChecker&gt;&amp;)::'lambda'(Fortran::semantics::SemanticsVisitor&lt;Fortran::semantics::AllocateChecker, Fortran::semantics::ArithmeticIfStmtChecker, Fortran::semantics::AssignmentChecker, Fortran::semantics::CaseChecker, Fortran::semantics::CoarrayChecker, Fortran::semantics::DataChecker, Fortran::semantics::DeallocateChecker, Fortran::semantics::DoForallChecker, Fortran::semantics::IfStmtChecker, Fortran::semantics::IoChecker, Fortran::semantics::MiscChecker, Fortran::semantics::NamelistChecker, Fortran::semantics::NullifyChecker, Fortran::semantics::PurityChecker, Fortran::semantics::ReturnStmtChecker, Fortran::semantics::SelectRankConstructChecker, Fortran::semantics::SelectTypeChecker, Fortran::semantics::StopChecker&gt; const&amp;), std::variant&lt;Fortran::common::Indirection&lt;Fortran::parser::MainProgram, false&gt;, Fortran::common::Indirection&lt;Fortran::parser::FunctionSubprogram, false&gt;, Fortran::common::Indirection&lt;Fortran::parser::SubroutineSubprogram, false&gt;, Fortran::common::Indirection&lt;Fortran::parser::Module, false&gt;, Fortran::common::Indirection&lt;Fortran::parser::Submodule, false&gt;, Fortran::common::Indirection&lt;Fortran::parser::BlockData, false&gt;, Fortran::common::Indirection&lt;Fortran::parser::CompilerDirective, false&gt;, Fortran::common::Indirection&lt;Fortran::parser::OpenACCRoutineConstruct, false&gt;&gt; const&amp;&gt;(void Fortran::parser::detail::ParseTreeVisitorLookupScope::Walk&lt;Fortran::semantics::SemanticsVisitor&lt;Fortran::semantics::AllocateChecker, Fortran::semantics::ArithmeticIfStmtChecker, Fortran::semantics::AssignmentChecker, Fortran::semantics::CaseChecker, Fortran::semantics::CoarrayChecker, Fortran::semantics::DataChecker, Fortran::semantics::DeallocateChecker, Fortran::semantics::DoForallChecker, Fortran::semantics::IfStmtChecker, Fortran::semantics::IoChecker, Fortran::semantics::MiscChecker, Fortran::semantics::NamelistChecker, Fortran::semantics::NullifyChecker, Fortran::semantics::PurityChecker, Fortran::semantics::ReturnStmtChecker, Fortran::semantics::SelectRankConstructChecker, Fortran::semantics::SelectTypeChecker, Fortran::semantics::StopChecker&gt;, Fortran::common::Indirection&lt;Fortran::parser::MainProgram, false&gt;, Fortran::common::Indirection&lt;Fortran::parser::FunctionSubprogram, false&gt;, Fortran::common::Indirection&lt;Fortran::parser::SubroutineSubprogram, false&gt;, Fortran::common::Indirection&lt;Fortran::parser::Module, false&gt;, Fortran::common::Indirection&lt;Fortran::parser::Submodule, false&gt;, Fortran::common::Indirection&lt;Fortran::parser::BlockData, false&gt;, Fortran::common::Indirection&lt;Fortran::parser::CompilerDirective, false&gt;, Fortran::common::Indirection&lt;Fortran::parser::OpenACCRoutineConstruct, false&gt;&gt;(std::variant&lt;Fortran::common::Indirection&lt;Fortran::parser::MainProgram, false&gt;, Fortran::common::Indirection&lt;Fortran::parser::FunctionSubprogram, false&gt;, Fortran::common::Indirection&lt;Fortran::parser::SubroutineSubprogram, false&gt;, Fortran::common::Indirection&lt;Fortran::parser::Module, false&gt;, Fortran::common::Indirection&lt;Fortran::parser::Submodule, false&gt;, Fortran::common::Indirection&lt;Fortran::parser::BlockData, false&gt;, Fortran::common::Indirection&lt;Fortran::parser::CompilerDirective, false&gt;, Fortran::common::Indirection&lt;Fortran::parser::OpenACCRoutineConstruct, false&gt;&gt; const&amp;, Fortran::semantics::SemanticsVisitor&lt;Fortran::semantics::AllocateChecker, Fortran::semantics::ArithmeticIfStmtChecker, Fortran::semantics::AssignmentChecker, Fortran::semantics::CaseChecker, Fortran::semantics::CoarrayChecker, Fortran::semantics::DataChecker, Fortran::semantics::DeallocateChecker, Fortran::semantics::DoForallChecker, Fortran::semantics::IfStmtChecker, Fortran::semantics::IoChecker, Fortran::semantics::MiscChecker, Fortran::semantics::NamelistChecker, Fortran::semantics::NullifyChecker, Fortran::semantics::PurityChecker, Fortran::semantics::ReturnStmtChecker, Fortran::semantics::SelectRankConstructChecker, Fortran::semantics::SelectTypeChecker, Fortran::semantics::StopChecker&gt;&amp;)::'lambda'(Fortran::semantics::SemanticsVisitor&lt;Fortran::semantics::AllocateChecker, Fortran::semantics::ArithmeticIfStmtChecker, Fortran::semantics::AssignmentChecker, Fortran::semantics::CaseChecker, Fortran::semantics::CoarrayChecker, Fortran::semantics::DataChecker, Fortran::semantics::DeallocateChecker, Fortran::semantics::DoForallChecker, Fortran::semantics::IfStmtChecker, Fortran::semantics::IoChecker, Fortran::semantics::MiscChecker, Fortran::semantics::NamelistChecker, Fortran::semantics::NullifyChecker, Fortran::semantics::PurityChecker, Fortran::semantics::ReturnStmtChecker, Fortran::semantics::SelectRankConstructChecker, Fortran::semantics::SelectTypeChecker, Fortran::semantics::StopChecker&gt; const&amp;)&amp;&amp;, unsigned long, std::variant&lt;Fortran::common::Indirection&lt;Fortran::parser::MainProgram, false&gt;, Fortran::common::Indirection&lt;Fortran::parser::FunctionSubprogram, false&gt;, Fortran::common::Indirection&lt;Fortran::parser::SubroutineSubprogram, false&gt;, Fortran::common::Indirection&lt;Fortran::parser::Module, false&gt;, Fortran::common::Indirection&lt;Fortran::parser::Submodule, false&gt;, Fortran::common::Indirection&lt;Fortran::parser::BlockData, false&gt;, Fortran::common::Indirection&lt;Fortran::parser::CompilerDirective, false&gt;, Fortran::common::Indirection&lt;Fortran::parser::OpenACCRoutineConstruct, false&gt;&gt; const&amp;) (/opt/compiler-explorer/clang-llvmflang-trunk-20250523/bin/flang+0x49d9845)
#<!-- -->12 0x00000000049f38d8 Fortran::semantics::Semantics::Perform() (/opt/compiler-explorer/clang-llvmflang-trunk-20250523/bin/flang+0x49f38d8)
#<!-- -->13 0x0000000003ed6588 Fortran::frontend::FrontendAction::runSemanticChecks() (/opt/compiler-explorer/clang-llvmflang-trunk-20250523/bin/flang+0x3ed6588)
#<!-- -->14 0x0000000004188250 Fortran::frontend::CodeGenAction::beginSourceFileAction() (/opt/compiler-explorer/clang-llvmflang-trunk-20250523/bin/flang+0x4188250)
#<!-- -->15 0x0000000003ed51c5 Fortran::frontend::FrontendAction::beginSourceFile(Fortran::frontend::CompilerInstance&amp;, Fortran::frontend::FrontendInputFile const&amp;) (/opt/compiler-explorer/clang-llvmflang-trunk-20250523/bin/flang+0x3ed51c5)
#<!-- -->16 0x0000000003ec3cc7 Fortran::frontend::CompilerInstance::executeAction(Fortran::frontend::FrontendAction&amp;) (/opt/compiler-explorer/clang-llvmflang-trunk-20250523/bin/flang+0x3ec3cc7)
#<!-- -->17 0x0000000003edeb33 Fortran::frontend::executeCompilerInvocation(Fortran::frontend::CompilerInstance*) (/opt/compiler-explorer/clang-llvmflang-trunk-20250523/bin/flang+0x3edeb33)
#<!-- -->18 0x00000000021ef16a fc1_main(llvm::ArrayRef&lt;char const*&gt;, char const*) (/opt/compiler-explorer/clang-llvmflang-trunk-20250523/bin/flang+0x21ef16a)
#<!-- -->19 0x00000000020a5fff main (/opt/compiler-explorer/clang-llvmflang-trunk-20250523/bin/flang+0x20a5fff)
#<!-- -->20 0x0000779d90229d90 (/lib/x86_64-linux-gnu/libc.so.6+0x29d90)
#<!-- -->21 0x0000779d90229e40 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x29e40)
#<!-- -->22 0x00000000021edb35 _start (/opt/compiler-explorer/clang-llvmflang-trunk-20250523/bin/flang+0x21edb35)
flang-21: error: unable to execute command: Aborted (core dumped)
flang-21: error: flang frontend command failed due to signal (use -v to see invocation)
flang version 21.0.0git (https://github.com/llvm/llvm-project.git d6596482ef277269dd35b5ea0c0439173cba7636)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /opt/compiler-explorer/clang-llvmflang-trunk-20250523/bin
flang-21: warning: OpenMP support in flang is still experimental [-Wexperimental-option]
flang-21: note: diagnostic msg: 
********************

PLEASE ATTACH THE FOLLOWING FILES TO THE BUG REPORT:
Preprocessed source(s) and associated run script(s) are located at:
flang-21: note: diagnostic msg: /tmp/example-20d2b4
flang-21: note: diagnostic msg: /tmp/example-20d2b4.sh
flang-21: note: diagnostic msg: 

********************
Compiler returned: 254