VLA in coroutine produces internal clang segfault

[kelbon]

Its obviously must be ill-formed to create VLA in corotuine, because itis not possible to determine frame size for such coro

void use(int*);
dd::generator<int> g(int i) {
    co_yield 1;
    int arr[i];
    use(arr);
}

https://godbolt.org/z/WoE94a4sf

compiler output

PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace, preprocessed source, and associated run script.
Stack dump:
0.	Program arguments: /opt/compiler-explorer/clang-16.0.0/bin/clang++ -gdwarf-4 -g -o /app/output.s -mllvm --x86-asm-syntax=intel -S --gcc-toolchain=/opt/compiler-explorer/gcc-12.2.0 -fcolor-diagnostics -fno-crash-diagnostics -std=c++20 -O3 -DNDEBUG <source>
1.	<eof> parser at end of file
2.	Optimizer
3.	While splitting coroutine @_Z1gi
 #0 0x000055f89f40e8df llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/opt/compiler-explorer/clang-16.0.0/bin/clang+++0x3ba18df)
 #1 0x000055f89f40c90c llvm::sys::CleanupOnSignal(unsigned long) (/opt/compiler-explorer/clang-16.0.0/bin/clang+++0x3b9f90c)
 #2 0x000055f89f35f518 CrashRecoverySignalHandler(int) CrashRecoveryContext.cpp:0:0
 #3 0x00007fee176a3420 __restore_rt (/lib/x86_64-linux-gnu/libpthread.so.0+0x14420)
 #4 0x000055f89ec3f4dc llvm::AllocaInst::getAllocationSize(llvm::DataLayout const&) const (/opt/compiler-explorer/clang-16.0.0/bin/clang+++0x33d24dc)
 #5 0x000055f8a09dbcc6 void std::__unguarded_linear_insert<(anonymous namespace)::AllocaInfo*, __gnu_cxx::__ops::_Val_comp_iter<(anonymous namespace)::FrameTypeBuilder::addFieldForAllocas(llvm::Function const&, (anonymous namespace)::FrameDataInfo&, llvm::coro::Shape&)::'lambda3'(auto const&, auto const&)>>(auto, auto) CoroFrame.cpp:0:0
 #6 0x000055f8a09dc0e8 void std::__insertion_sort<(anonymous namespace)::AllocaInfo*, __gnu_cxx::__ops::_Iter_comp_iter<(anonymous namespace)::FrameTypeBuilder::addFieldForAllocas(llvm::Function const&, (anonymous namespace)::FrameDataInfo&, llvm::coro::Shape&)::'lambda3'(auto const&, auto const&)>>(auto, auto, auto) CoroFrame.cpp:0:0
 #7 0x000055f8a09de6fc buildFrameType(llvm::Function&, llvm::coro::Shape&, (anonymous namespace)::FrameDataInfo&) CoroFrame.cpp:0:0
 #8 0x000055f8a09e6409 llvm::coro::buildCoroutineFrame(llvm::Function&, llvm::coro::Shape&) (/opt/compiler-explorer/clang-16.0.0/bin/clang+++0x5179409)
 #9 0x000055f8a09c88cc llvm::CoroSplitPass::run(llvm::LazyCallGraph::SCC&, llvm::AnalysisManager<llvm::LazyCallGraph::SCC, llvm::LazyCallGraph&>&, llvm::LazyCallGraph&, llvm::CGSCCUpdateResult&) (/opt/compiler-explorer/clang-16.0.0/bin/clang+++0x515b8cc)
#10 0x000055f8a08cde66 llvm::detail::PassModel<llvm::LazyCallGraph::SCC, llvm::CoroSplitPass, llvm::PreservedAnalyses, llvm::AnalysisManager<llvm::LazyCallGraph::SCC, llvm::LazyCallGraph&>, llvm::LazyCallGraph&, llvm::CGSCCUpdateResult&>::run(llvm::LazyCallGraph::SCC&, llvm::AnalysisManager<llvm::LazyCallGraph::SCC, llvm::LazyCallGraph&>&, llvm::LazyCallGraph&, llvm::CGSCCUpdateResult&) (/opt/compiler-explorer/clang-16.0.0/bin/clang+++0x5060e66)
#11 0x000055f89e348724 llvm::PassManager<llvm::LazyCallGraph::SCC, llvm::AnalysisManager<llvm::LazyCallGraph::SCC, llvm::LazyCallGraph&>, llvm::LazyCallGraph&, llvm::CGSCCUpdateResult&>::run(llvm::LazyCallGraph::SCC&, llvm::AnalysisManager<llvm::LazyCallGraph::SCC, llvm::LazyCallGraph&>&, llvm::LazyCallGraph&, llvm::CGSCCUpdateResult&) (/opt/compiler-explorer/clang-16.0.0/bin/clang+++0x2adb724)
#12 0x000055f89edecee6 llvm::detail::PassModel<llvm::LazyCallGraph::SCC, llvm::PassManager<llvm::LazyCallGraph::SCC, llvm::AnalysisManager<llvm::LazyCallGraph::SCC, llvm::LazyCallGraph&>, llvm::LazyCallGraph&, llvm::CGSCCUpdateResult&>, llvm::PreservedAnalyses, llvm::AnalysisManager<llvm::LazyCallGraph::SCC, llvm::LazyCallGraph&>, llvm::LazyCallGraph&, llvm::CGSCCUpdateResult&>::run(llvm::LazyCallGraph::SCC&, llvm::AnalysisManager<llvm::LazyCallGraph::SCC, llvm::LazyCallGraph&>&, llvm::LazyCallGraph&, llvm::CGSCCUpdateResult&) (/opt/compiler-explorer/clang-16.0.0/bin/clang+++0x357fee6)
#13 0x000055f89e34c3be llvm::DevirtSCCRepeatedPass::run(llvm::LazyCallGraph::SCC&, llvm::AnalysisManager<llvm::LazyCallGraph::SCC, llvm::LazyCallGraph&>&, llvm::LazyCallGraph&, llvm::CGSCCUpdateResult&) (/opt/compiler-explorer/clang-16.0.0/bin/clang+++0x2adf3be)
#14 0x000055f89edece96 llvm::detail::PassModel<llvm::LazyCallGraph::SCC, llvm::DevirtSCCRepeatedPass, llvm::PreservedAnalyses, llvm::AnalysisManager<llvm::LazyCallGraph::SCC, llvm::LazyCallGraph&>, llvm::LazyCallGraph&, llvm::CGSCCUpdateResult&>::run(llvm::LazyCallGraph::SCC&, llvm::AnalysisManager<llvm::LazyCallGraph::SCC, llvm::LazyCallGraph&>&, llvm::LazyCallGraph&, llvm::CGSCCUpdateResult&) (/opt/compiler-explorer/clang-16.0.0/bin/clang+++0x357fe96)
#15 0x000055f89e3498bb llvm::ModuleToPostOrderCGSCCPassAdaptor::run(llvm::Module&, llvm::AnalysisManager<llvm::Module>&) (/opt/compiler-explorer/clang-16.0.0/bin/clang+++0x2adc8bb)
#16 0x000055f89edf4e3d llvm::ModuleInlinerWrapperPass::run(llvm::Module&, llvm::AnalysisManager<llvm::Module>&) (/opt/compiler-explorer/clang-16.0.0/bin/clang+++0x3587e3d)
#17 0x000055f8a0771196 llvm::detail::PassModel<llvm::Module, llvm::ModuleInlinerWrapperPass, llvm::PreservedAnalyses, llvm::AnalysisManager<llvm::Module>>::run(llvm::Module&, llvm::AnalysisManager<llvm::Module>&) (/opt/compiler-explorer/clang-16.0.0/bin/clang+++0x4f04196)
#18 0x000055f89ecbffb9 llvm::PassManager<llvm::Module, llvm::AnalysisManager<llvm::Module>>::run(llvm::Module&, llvm::AnalysisManager<llvm::Module>&) (/opt/compiler-explorer/clang-16.0.0/bin/clang+++0x3452fb9)
#19 0x000055f89f7f1b44 (anonymous namespace)::EmitAssemblyHelper::RunOptimizationPipeline(clang::BackendAction, std::unique_ptr<llvm::raw_pwrite_stream, std::default_delete<llvm::raw_pwrite_stream>>&, std::unique_ptr<llvm::ToolOutputFile, std::default_delete<llvm::ToolOutputFile>>&) BackendUtil.cpp:0:0
#20 0x000055f89f7f4bd6 clang::EmitBackendOutput(clang::DiagnosticsEngine&, clang::HeaderSearchOptions const&, clang::CodeGenOptions const&, clang::TargetOptions const&, clang::LangOptions const&, llvm::StringRef, llvm::Module*, clang::BackendAction, std::unique_ptr<llvm::raw_pwrite_stream, std::default_delete<llvm::raw_pwrite_stream>>) (/opt/compiler-explorer/clang-16.0.0/bin/clang+++0x3f87bd6)
#21 0x000055f8a06ff238 clang::BackendConsumer::HandleTranslationUnit(clang::ASTContext&) (/opt/compiler-explorer/clang-16.0.0/bin/clang+++0x4e92238)
#22 0x000055f8a1923d5d clang::ParseAST(clang::Sema&, bool, bool) (/opt/compiler-explorer/clang-16.0.0/bin/clang+++0x60b6d5d)
#23 0x000055f8a06fe865 clang::CodeGenAction::ExecuteAction() (/opt/compiler-explorer/clang-16.0.0/bin/clang+++0x4e91865)
#24 0x000055f89ffda671 clang::FrontendAction::Execute() (/opt/compiler-explorer/clang-16.0.0/bin/clang+++0x476d671)
#25 0x000055f89ff5e993 clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/opt/compiler-explorer/clang-16.0.0/bin/clang+++0x46f1993)
#26 0x000055f8a00beb3b clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/opt/compiler-explorer/clang-16.0.0/bin/clang+++0x4851b3b)
#27 0x000055f89cbe741c cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (/opt/compiler-explorer/clang-16.0.0/bin/clang+++0x137a41c)
#28 0x000055f89cbe2bdc ExecuteCC1Tool(llvm::SmallVectorImpl<char const*>&) driver.cpp:0:0
#29 0x000055f89fdbfce9 void llvm::function_ref<void ()>::callback_fn<clang::driver::CC1Command::Execute(llvm::ArrayRef<std::optional<llvm::StringRef>>, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>*, bool*) const::'lambda'()>(long) Job.cpp:0:0
#30 0x000055f89f35f977 llvm::CrashRecoveryContext::RunSafely(llvm::function_ref<void ()>) (/opt/compiler-explorer/clang-16.0.0/bin/clang+++0x3af2977)
#31 0x000055f89fdbff1c clang::driver::CC1Command::Execute(llvm::ArrayRef<std::optional<llvm::StringRef>>, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>*, bool*) const (.part.0) Job.cpp:0:0
#32 0x000055f89fd883fc clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&, clang::driver::Command const*&, bool) const (/opt/compiler-explorer/clang-16.0.0/bin/clang+++0x451b3fc)
#33 0x000055f89fd88ded clang::driver::Compilation::ExecuteJobs(clang::driver::JobList const&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&, bool) const (/opt/compiler-explorer/clang-16.0.0/bin/clang+++0x451bded)
#34 0x000055f89fd9323c clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&) (/opt/compiler-explorer/clang-16.0.0/bin/clang+++0x452623c)
#35 0x000055f89cbe5523 clang_main(int, char**) (/opt/compiler-explorer/clang-16.0.0/bin/clang+++0x1378523)
#36 0x00007fee17151083 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x24083)
#37 0x000055f89cbded1e _start (/opt/compiler-explorer/clang-16.0.0/bin/clang+++0x1371d1e)
clang-16: error: clang frontend command failed with exit code 139 (use -v to see invocation)
Compiler returned: 139

[kelbon]

on clang trunk it produces 'backend error' with code 70 and still with dump, okay its obviously implementation limitation now

P.S. it must be ill formed only in case when it's required to store VLA between awaits, in this case there are no logical problem to use VLA

[shafik]

CC @ChuanqiXu9

[llvmbot]

@llvm/issue-subscribers-clang-frontend

[llvmbot]

@llvm/issue-subscribers-coroutines

[cor3ntin]

in Sema::CheckCompletedCoroutineBody we do:

  // [stmt.return.coroutine]p1:
  //   A coroutine shall not enclose a return statement ([stmt.return]).
  if (Fn->FirstReturnLoc.isValid()) {
    assert(Fn->FirstCoroutineStmtLoc.isValid() &&
                   "first coroutine location not set");
    Diag(Fn->FirstReturnLoc, diag::err_return_in_coroutine);
    Diag(Fn->FirstCoroutineStmtLoc, diag::note_declared_coroutine_here)
            << Fn->getFirstCoroutineStmtKeyword();
  }

Doing the same thing for VLAS would resolve the crash.

in Sema::CheckVariableDeclarationType we check that VLAS are not declared at file scope.
This seems like a good place to set a flag on the function scope info getEnclosingFunction, indicating we found a VLA

[llvmbot]

Hi!

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4. Create a git commit
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[ChuanqiXu9]

Assign to myself to add this to my TODO list. Feel free to take this if any one is interested.