Clang 19.1.7 crash during lambda compilation with naked attribute

[alpluspluss]

Version: 19.1.7
Host OS: macOS Sonoma 14.4
Flags: -ffreestanding -mcmodel=kernel
Target: x86_64-none-elf

Code:

/* syscall entry point */
static auto syscall_entry = []() __attribute__((naked))
{
    asm volatile(
        "swapgs\n"
        "movq %rsp, %gs:16\n"
        "movq %gs:8, %rsp\n"
        "ret"
    );
};

I happened to run into a crash when compiling kernel code using a lambda with __attribute__((naked)).
This code doesn't crash during compilation with x86_64-elf-g++. I may be able to contribute a fix for this issue if needed.

Link to the attached file as I am not able to attach it normally: https://pastebin.com/GzeB8ga7

[alpluspluss]

Another one. This is small enough to fit in here without obscuring anyone.

# Crash reproducer for Homebrew clang version 19.1.7
# Driver args: "--driver-mode=g++" "-ffreestanding" "-O3" "-march=x86-64" "-mcmodel=kernel" "-mgeneral-regs-only" "-mno-red-zone" "--target=x86_64-none-elf" "-fno-exceptions" "-fno-rtti" "-I" "x86_64/include" "-I" "/Users/tand/Desktop/projects/kafka/include" "-c" "x86_64/src/X86cpu.cpp" "-o" "/Users/tand/Desktop/projects/kafka/build/obj/arch-x86_64/x86_64-X86cpu.o"
# Original command:  "/opt/homebrew/Cellar/llvm/19.1.7_1/bin/clang-19" "-cc1" "-triple" "x86_64-unknown-none-elf" "-emit-obj" "-disable-free" "-clear-ast-before-backend" "-disable-llvm-verifier" "-discard-value-names" "-main-file-name" "X86cpu.cpp" "-mrelocation-model" "static" "-mframe-pointer=all" "-fmath-errno" "-ffp-contract=on" "-fno-rounding-math" "-mconstructor-aliases" "-ffreestanding" "-mcmodel=kernel" "-target-cpu" "x86-64" "-target-feature" "-x87" "-target-feature" "-mmx" "-target-feature" "-sse" "-disable-red-zone" "-debugger-tuning=gdb" "-fdebug-compilation-dir=/Users/tand/Desktop/projects/kafka/arch" "-target-linker-version" "1115.7.3" "-fcoverage-compilation-dir=/Users/tand/Desktop/projects/kafka/arch" "-resource-dir" "/opt/homebrew/Cellar/llvm/19.1.7_1/lib/clang/19" "-I" "x86_64/include" "-I" "/Users/tand/Desktop/projects/kafka/include" "-I/opt/homebrew/opt/llvm/include" "-I/opt/homebrew/include" "-O3" "-fdeprecated-macro" "-ferror-limit" "19" "-fno-rtti" "-fgnuc-version=4.2.1" "-fskip-odr-check-in-gmf" "-fcolor-diagnostics" "-vectorize-loops" "-vectorize-slp" "-faddrsig" "-o" "/Users/tand/Desktop/projects/kafka/build/obj/arch-x86_64/x86_64-X86cpu.o" "-x" "c++" "x86_64/src/X86cpu.cpp"
 "/opt/homebrew/Cellar/llvm/19.1.7_1/bin/clang-19" "-cc1" "-triple" "x86_64-unknown-none-elf" "-emit-obj" "-disable-free" "-clear-ast-before-backend" "-disable-llvm-verifier" "-discard-value-names" "-main-file-name" "X86cpu.cpp" "-mrelocation-model" "static" "-mframe-pointer=all" "-fmath-errno" "-ffp-contract=on" "-fno-rounding-math" "-mconstructor-aliases" "-ffreestanding" "-mcmodel=kernel" "-target-cpu" "x86-64" "-target-feature" "-x87" "-target-feature" "-mmx" "-target-feature" "-sse" "-disable-red-zone" "-debugger-tuning=gdb" "-fdebug-compilation-dir=/Users/tand/Desktop/projects/kafka/arch" "-target-linker-version" "1115.7.3" "-fcoverage-compilation-dir=/Users/tand/Desktop/projects/kafka/arch" "-O3" "-fdeprecated-macro" "-ferror-limit" "19" "-fno-rtti" "-fgnuc-version=4.2.1" "-fskip-odr-check-in-gmf" "-fcolor-diagnostics" "-vectorize-loops" "-vectorize-slp" "-faddrsig" "-x" "c++" "X86cpu-27423a.cpp"

[EugeneZelenko]

Could you please try 20 or main branch?

[alpluspluss]

@EugeneZelenko Yes, I can do release/20

[frederick-vs-ja]

I added a test function to call the lambda to reproduce the crash (Godbolt link)

/* syscall entry point */
static auto syscall_entry = []() __attribute__((naked))
{
    asm volatile(
        "swapgs\n"
        "movq %rsp, %gs:16\n"
        "movq %gs:8, %rsp\n"
        "ret"
    );
};

void test()
{
    syscall_entry();
}

clang++: /root/llvm-project/clang/lib/CodeGen/CodeGenFunction.h:3043: clang::CodeGen::Address clang::CodeGen::CodeGenFunction::GetAddrOfLocalVar(const clang::VarDecl*): Assertion `it != LocalDeclMap.end() && "Invalid argument to GetAddrOfLocalVar(), no decl!"' failed.
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-assertions-trunk/bin/clang++ -gdwarf-4 -g -o /app/output.s -mllvm --x86-asm-syntax=intel -fno-verbose-asm -S --gcc-toolchain=/opt/compiler-explorer/gcc-snapshot -fcolor-diagnostics -fno-crash-diagnostics -std=c++20 -pedantic-errors -ffreestanding -mcmodel=kernel <source>
1.	<eof> parser at end of file
2.	Per-file LLVM IR generation
3.	<source>:2:29: Generating code for declaration '(anonymous class)::operator()'
 #0 0x0000000003e9da68 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3e9da68)
 #1 0x0000000003e9b6f4 llvm::sys::CleanupOnSignal(unsigned long) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3e9b6f4)
 #2 0x0000000003de0ae8 CrashRecoverySignalHandler(int) CrashRecoveryContext.cpp:0:0
 #3 0x0000737cfec42520 (/lib/x86_64-linux-gnu/libc.so.6+0x42520)
 #4 0x0000737cfec969fc pthread_kill (/lib/x86_64-linux-gnu/libc.so.6+0x969fc)
 #5 0x0000737cfec42476 gsignal (/lib/x86_64-linux-gnu/libc.so.6+0x42476)
 #6 0x0000737cfec287f3 abort (/lib/x86_64-linux-gnu/libc.so.6+0x287f3)
 #7 0x0000737cfec2871b (/lib/x86_64-linux-gnu/libc.so.6+0x2871b)
 #8 0x0000737cfec39e96 (/lib/x86_64-linux-gnu/libc.so.6+0x39e96)
 #9 0x0000000004727b8d clang::CodeGen::CGCXXABI::loadIncomingCXXThis(clang::CodeGen::CodeGenFunction&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4727b8d)
#10 0x00000000044c5618 (anonymous namespace)::ItaniumCXXABI::EmitInstanceFunctionProlog(clang::CodeGen::CodeGenFunction&) ItaniumCXXABI.cpp:0:0
#11 0x00000000043eca0c clang::CodeGen::CodeGenFunction::StartFunction(clang::GlobalDecl, clang::QualType, llvm::Function*, clang::CodeGen::CGFunctionInfo const&, clang::CodeGen::FunctionArgList const&, clang::SourceLocation, clang::SourceLocation) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x43eca0c)
#12 0x00000000043f02b1 clang::CodeGen::CodeGenFunction::GenerateCode(clang::GlobalDecl, llvm::Function*, clang::CodeGen::CGFunctionInfo const&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x43f02b1)
#13 0x000000000445975a clang::CodeGen::CodeGenModule::EmitGlobalFunctionDefinition(clang::GlobalDecl, llvm::GlobalValue*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x445975a)
#14 0x00000000044549a4 clang::CodeGen::CodeGenModule::EmitGlobalDefinition(clang::GlobalDecl, llvm::GlobalValue*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x44549a4)
#15 0x00000000044608dd clang::CodeGen::CodeGenModule::EmitDeferred() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x44608dd)
#16 0x0000000004462c03 clang::CodeGen::CodeGenModule::Release() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4462c03)
#17 0x000000000483426e (anonymous namespace)::CodeGeneratorImpl::HandleTranslationUnit(clang::ASTContext&) ModuleBuilder.cpp:0:0
#18 0x0000000004830715 clang::BackendConsumer::HandleTranslationUnit(clang::ASTContext&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4830715)
#19 0x00000000064c4b7c clang::ParseAST(clang::Sema&, bool, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x64c4b7c)
#20 0x0000000004830ec8 clang::CodeGenAction::ExecuteAction() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4830ec8)
#21 0x0000000004b1ef35 clang::FrontendAction::Execute() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4b1ef35)
#22 0x0000000004aa0bce clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4aa0bce)
#23 0x0000000004c0f3de clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4c0f3de)
#24 0x0000000000d5b75f cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xd5b75f)
#25 0x0000000000d52f1a ExecuteCC1Tool(llvm::SmallVectorImpl<char const*>&, llvm::ToolContext const&) driver.cpp:0:0
#26 0x0000000004896649 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
#27 0x0000000003de0f84 llvm::CrashRecoveryContext::RunSafely(llvm::function_ref<void ()>) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3de0f84)
#28 0x0000000004896c5f 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
#29 0x000000000485961d clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&, clang::driver::Command const*&, bool) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x485961d)
#30 0x000000000485a6ae clang::driver::Compilation::ExecuteJobs(clang::driver::JobList const&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&, bool) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x485a6ae)
#31 0x0000000004861db5 clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4861db5)
#32 0x0000000000d58558 clang_main(int, char**, llvm::ToolContext const&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xd58558)
#33 0x0000000000c1f1f4 main (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xc1f1f4)
#34 0x0000737cfec29d90 (/lib/x86_64-linux-gnu/libc.so.6+0x29d90)
#35 0x0000737cfec29e40 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x29e40)
#36 0x0000000000d529c5 _start (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xd529c5)
clang++: error: clang frontend command failed with exit code 134 (use -v to see invocation)
Compiler returned: 134

Clang 19 crash

Godbolt link

clang++: /root/llvm-project/clang/lib/CodeGen/CodeGenFunction.h:2984: clang::CodeGen::Address clang::CodeGen::CodeGenFunction::GetAddrOfLocalVar(const clang::VarDecl*): Assertion `it != LocalDeclMap.end() && "Invalid argument to GetAddrOfLocalVar(), no decl!"' failed.
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-assertions-19.1.0/bin/clang++ -gdwarf-4 -g -o /app/output.s -mllvm --x86-asm-syntax=intel -fno-verbose-asm -S --gcc-toolchain=/opt/compiler-explorer/gcc-14.2.0 -fcolor-diagnostics -fno-crash-diagnostics -std=c++20 -pedantic-errors -ffreestanding -mcmodel=kernel <source>
1.	<eof> parser at end of file
2.	Per-file LLVM IR generation
3.	<source>:2:29: Generating code for declaration '(anonymous class)::operator()'
 #0 0x0000000003ae9978 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/opt/compiler-explorer/clang-assertions-19.1.0/bin/clang+++0x3ae9978)
 #1 0x0000000003ae766c llvm::sys::CleanupOnSignal(unsigned long) (/opt/compiler-explorer/clang-assertions-19.1.0/bin/clang+++0x3ae766c)
 #2 0x0000000003a308f8 CrashRecoverySignalHandler(int) CrashRecoveryContext.cpp:0:0
 #3 0x000076522cc42520 (/lib/x86_64-linux-gnu/libc.so.6+0x42520)
 #4 0x000076522cc969fc pthread_kill (/lib/x86_64-linux-gnu/libc.so.6+0x969fc)
 #5 0x000076522cc42476 gsignal (/lib/x86_64-linux-gnu/libc.so.6+0x42476)
 #6 0x000076522cc287f3 abort (/lib/x86_64-linux-gnu/libc.so.6+0x287f3)
 #7 0x000076522cc2871b (/lib/x86_64-linux-gnu/libc.so.6+0x2871b)
 #8 0x000076522cc39e96 (/lib/x86_64-linux-gnu/libc.so.6+0x39e96)
 #9 0x00000000041c68fd clang::CodeGen::CGCXXABI::loadIncomingCXXThis(clang::CodeGen::CodeGenFunction&) (/opt/compiler-explorer/clang-assertions-19.1.0/bin/clang+++0x41c68fd)
#10 0x0000000003f9acd8 (anonymous namespace)::ItaniumCXXABI::EmitInstanceFunctionProlog(clang::CodeGen::CodeGenFunction&) ItaniumCXXABI.cpp:0:0
#11 0x0000000003ec9ff5 clang::CodeGen::CodeGenFunction::StartFunction(clang::GlobalDecl, clang::QualType, llvm::Function*, clang::CodeGen::CGFunctionInfo const&, clang::CodeGen::FunctionArgList const&, clang::SourceLocation, clang::SourceLocation) (/opt/compiler-explorer/clang-assertions-19.1.0/bin/clang+++0x3ec9ff5)
#12 0x0000000003ecd987 clang::CodeGen::CodeGenFunction::GenerateCode(clang::GlobalDecl, llvm::Function*, clang::CodeGen::CGFunctionInfo const&) (/opt/compiler-explorer/clang-assertions-19.1.0/bin/clang+++0x3ecd987)
#13 0x0000000003f2de52 clang::CodeGen::CodeGenModule::EmitGlobalFunctionDefinition(clang::GlobalDecl, llvm::GlobalValue*) (/opt/compiler-explorer/clang-assertions-19.1.0/bin/clang+++0x3f2de52)
#14 0x0000000003f28d65 clang::CodeGen::CodeGenModule::EmitGlobalDefinition(clang::GlobalDecl, llvm::GlobalValue*) (/opt/compiler-explorer/clang-assertions-19.1.0/bin/clang+++0x3f28d65)
#15 0x0000000003f34cbd clang::CodeGen::CodeGenModule::EmitDeferred() (/opt/compiler-explorer/clang-assertions-19.1.0/bin/clang+++0x3f34cbd)
#16 0x0000000003f36da3 clang::CodeGen::CodeGenModule::Release() (/opt/compiler-explorer/clang-assertions-19.1.0/bin/clang+++0x3f36da3)
#17 0x00000000043fb06e (anonymous namespace)::CodeGeneratorImpl::HandleTranslationUnit(clang::ASTContext&) ModuleBuilder.cpp:0:0
#18 0x00000000043f8cb5 clang::BackendConsumer::HandleTranslationUnit(clang::ASTContext&) (/opt/compiler-explorer/clang-assertions-19.1.0/bin/clang+++0x43f8cb5)
#19 0x00000000064cc55c clang::ParseAST(clang::Sema&, bool, bool) (/opt/compiler-explorer/clang-assertions-19.1.0/bin/clang+++0x64cc55c)
#20 0x00000000043f9448 clang::CodeGenAction::ExecuteAction() (/opt/compiler-explorer/clang-assertions-19.1.0/bin/clang+++0x43f9448)
#21 0x0000000004684f59 clang::FrontendAction::Execute() (/opt/compiler-explorer/clang-assertions-19.1.0/bin/clang+++0x4684f59)
#22 0x0000000004609f8e clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/opt/compiler-explorer/clang-assertions-19.1.0/bin/clang+++0x4609f8e)
#23 0x000000000476e2be clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/opt/compiler-explorer/clang-assertions-19.1.0/bin/clang+++0x476e2be)
#24 0x0000000000c82b7f cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (/opt/compiler-explorer/clang-assertions-19.1.0/bin/clang+++0xc82b7f)
#25 0x0000000000c7bcda ExecuteCC1Tool(llvm::SmallVectorImpl<char const*>&, llvm::ToolContext const&) driver.cpp:0:0
#26 0x000000000443cba9 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
#27 0x0000000003a30da4 llvm::CrashRecoveryContext::RunSafely(llvm::function_ref<void ()>) (/opt/compiler-explorer/clang-assertions-19.1.0/bin/clang+++0x3a30da4)
#28 0x000000000443d19f 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
#29 0x0000000004402c05 clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&, clang::driver::Command const*&, bool) const (/opt/compiler-explorer/clang-assertions-19.1.0/bin/clang+++0x4402c05)
#30 0x000000000440366d clang::driver::Compilation::ExecuteJobs(clang::driver::JobList const&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&, bool) const (/opt/compiler-explorer/clang-assertions-19.1.0/bin/clang+++0x440366d)
#31 0x000000000440b075 clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&) (/opt/compiler-explorer/clang-assertions-19.1.0/bin/clang+++0x440b075)
#32 0x0000000000c7fe95 clang_main(int, char**, llvm::ToolContext const&) (/opt/compiler-explorer/clang-assertions-19.1.0/bin/clang+++0xc7fe95)
#33 0x0000000000b547a4 main (/opt/compiler-explorer/clang-assertions-19.1.0/bin/clang+++0xb547a4)
#34 0x000076522cc29d90 (/lib/x86_64-linux-gnu/libc.so.6+0x29d90)
#35 0x000076522cc29e40 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x29e40)
#36 0x0000000000c7b78e _start (/opt/compiler-explorer/clang-assertions-19.1.0/bin/clang+++0xc7b78e)
clang++: error: clang frontend command failed with exit code 134 (use -v to see invocation)
Compiler returned: 134

Are these rough the same errors you encountered?

---

The crash seems to be lambda-specific. Godbolt link.

struct LambdaLike {
    [[gnu::naked]] void operator()() const {
        asm volatile(
            "swapgs\n"
            "movq %rsp, %gs:16\n"
            "movq %gs:8, %rsp\n"
            "ret"
        );
    }
};

static LambdaLike lambda_like_var;

void test()
{
    lambda_like_var();
}

[llvmbot]

@llvm/issue-subscribers-clang-codegen

Author: Al (alpluspluss)

Version: 19.1.7 Host OS: macOS Sonoma 14.4 Flags: -ffreestanding -mcmodel=kernel Target: x86_64-none-elf

Code:

/* syscall entry point */
static auto syscall_entry = []() __attribute__((naked))
{
    asm volatile(
        "swapgs\n"
        "movq %rsp, %gs:16\n"
        "movq %gs:8, %rsp\n"
        "ret"
    );
};

I happened to run into a crash when compiling kernel code using a lambda with __attribute__((naked)).
This code doesn't crash during compilation with x86_64-elf-g++. I may be able to contribute a fix for this issue if needed.

Link to the attached file as I am not able to attach it normally: https://pastebin.com/GzeB8ga7

[alpluspluss]

Yes. It looks almost the same if we ignore other details.