[clang] crash caused by a slightly modified libc++ std::source_location (in nostd) as a template argument

[Qwinci]

Stack dump:
0.	Program arguments: /usr/lib/llvm/15/bin/clang++ -I/home/visa/CLionProjects/crescent/src -I/home/visa/CLionProjects/crescent/thirdparty -g -fPIE -fcolor-diagnostics -Wall -fno-stack-protector -mno-80387 -mno-mmx -mno-sse -mno-sse2 -mno-red-zone -mgeneral-regs-only -mcmodel=kernel -masm=intel -fno-omit-frame-pointer -Wno-interrupt-service-routine -nostdlibinc -fno-exceptions -fno-rtti -std=gnu++2b -MD -MT CMakeFiles/crescent.dir/src/memory/allocator.cpp.o -MF CMakeFiles/crescent.dir/src/memory/allocator.cpp.o.d -o CMakeFiles/crescent.dir/src/memory/allocator.cpp.o -c /home/visa/CLionProjects/crescent/src/memory/allocator.cpp
1.	/home/visa/CLionProjects/crescent/src/memory/allocator.cpp:63:1: current parser token 'void'
2.	/home/visa/CLionProjects/crescent/src/memory/allocator.cpp:26:18: LLVM IR generation of declaration 'Allocator::alloc'
3.	/home/visa/CLionProjects/crescent/src/memory/allocator.cpp:26:18: Generating code for declaration 'Allocator::alloc'
4.	/home/visa/CLionProjects/crescent/src/utils/panic.hpp:32:33: Mangling declaration 'panic'
 #0 0x00007f4b6204c153 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/usr/lib/llvm/15/bin/../lib64/libLLVM-15.so+0x364c153)
 #1 0x00007f4b6204a292 llvm::sys::RunSignalHandlers() (/usr/lib/llvm/15/bin/../lib64/libLLVM-15.so+0x364a292)
 #2 0x00007f4b61f6c266 (/usr/lib/llvm/15/bin/../lib64/libLLVM-15.so+0x356c266)
 #3 0x00007f4b65468950 (/lib64/libc.so.6+0x37950)
 #4 0x00007f4b66f7293b (/usr/lib/llvm/15/bin/../lib64/libclang-cpp.so.15+0x197293b)
 #5 0x00007f4b66f80c60 (/usr/lib/llvm/15/bin/../lib64/libclang-cpp.so.15+0x1980c60)
 #6 0x00007f4b66f807d7 (/usr/lib/llvm/15/bin/../lib64/libclang-cpp.so.15+0x19807d7)
 #7 0x00007f4b66f7dacb (/usr/lib/llvm/15/bin/../lib64/libclang-cpp.so.15+0x197dacb)
 #8 0x00007f4b66f81706 (/usr/lib/llvm/15/bin/../lib64/libclang-cpp.so.15+0x1981706)
 #9 0x00007f4b66f73fc7 (/usr/lib/llvm/15/bin/../lib64/libclang-cpp.so.15+0x1973fc7)
#10 0x00007f4b66f72d7d (/usr/lib/llvm/15/bin/../lib64/libclang-cpp.so.15+0x1972d7d)
#11 0x00007f4b66f700bc (/usr/lib/llvm/15/bin/../lib64/libclang-cpp.so.15+0x19700bc)
#12 0x00007f4b67d3482a (/usr/lib/llvm/15/bin/../lib64/libclang-cpp.so.15+0x273482a)
#13 0x00007f4b67d2e96d clang::CodeGen::CodeGenModule::getMangledName(clang::GlobalDecl) (/usr/lib/llvm/15/bin/../lib64/libclang-cpp.so.15+0x272e96d)
#14 0x00007f4b67d43ccd clang::CodeGen::CodeGenModule::GetAddrOfFunction(clang::GlobalDecl, llvm::Type*, bool, bool, clang::CodeGen::ForDefinition_t) (/usr/lib/llvm/15/bin/../lib64/libclang-cpp.so.15+0x2743ccd)
#15 0x00007f4b67b8b614 (/usr/lib/llvm/15/bin/../lib64/libclang-cpp.so.15+0x258b614)
#16 0x00007f4b67b8a3b3 (/usr/lib/llvm/15/bin/../lib64/libclang-cpp.so.15+0x258a3b3)
#17 0x00007f4b67b891d7 clang::CodeGen::CodeGenFunction::EmitCallee(clang::Expr const*) (/usr/lib/llvm/15/bin/../lib64/libclang-cpp.so.15+0x25891d7)
#18 0x00007f4b67b88e5c clang::CodeGen::CodeGenFunction::EmitCallExpr(clang::CallExpr const*, clang::CodeGen::ReturnValueSlot) (/usr/lib/llvm/15/bin/../lib64/libclang-cpp.so.15+0x2588e5c)
#19 0x00007f4b67bc666d (/usr/lib/llvm/15/bin/../lib64/libclang-cpp.so.15+0x25c666d)
#20 0x00007f4b67bb9e9b clang::CodeGen::CodeGenFunction::EmitScalarExpr(clang::Expr const*, bool) (/usr/lib/llvm/15/bin/../lib64/libclang-cpp.so.15+0x25b9e9b)
#21 0x00007f4b67b6ea7e clang::CodeGen::CodeGenFunction::EmitAnyExpr(clang::Expr const*, clang::CodeGen::AggValueSlot, bool) (/usr/lib/llvm/15/bin/../lib64/libclang-cpp.so.15+0x256ea7e)
#22 0x00007f4b67b6e940 clang::CodeGen::CodeGenFunction::EmitIgnoredExpr(clang::Expr const*) (/usr/lib/llvm/15/bin/../lib64/libclang-cpp.so.15+0x256e940)
#23 0x00007f4b67cbf1a8 clang::CodeGen::CodeGenFunction::EmitStmt(clang::Stmt const*, llvm::ArrayRef<clang::Attr const*>) (/usr/lib/llvm/15/bin/../lib64/libclang-cpp.so.15+0x26bf1a8)
#24 0x00007f4b67cc004f clang::CodeGen::CodeGenFunction::EmitIfStmt(clang::IfStmt const&) (/usr/lib/llvm/15/bin/../lib64/libclang-cpp.so.15+0x26c004f)
#25 0x00007f4b67cbf2ec clang::CodeGen::CodeGenFunction::EmitStmt(clang::Stmt const*, llvm::ArrayRef<clang::Attr const*>) (/usr/lib/llvm/15/bin/../lib64/libclang-cpp.so.15+0x26bf2ec)
#26 0x00007f4b67cca8ac clang::CodeGen::CodeGenFunction::EmitCompoundStmtWithoutScope(clang::CompoundStmt const&, bool, clang::CodeGen::AggValueSlot) (/usr/lib/llvm/15/bin/../lib64/libclang-cpp.so.15+0x26ca8ac)
#27 0x00007f4b67d23c8e clang::CodeGen::CodeGenFunction::EmitFunctionBody(clang::Stmt const*) (/usr/lib/llvm/15/bin/../lib64/libclang-cpp.so.15+0x2723c8e)
#28 0x00007f4b67d2467c clang::CodeGen::CodeGenFunction::GenerateCode(clang::GlobalDecl, llvm::Function*, clang::CodeGen::CGFunctionInfo const&) (/usr/lib/llvm/15/bin/../lib64/libclang-cpp.so.15+0x272467c)
#29 0x00007f4b67d424fd clang::CodeGen::CodeGenModule::EmitGlobalFunctionDefinition(clang::GlobalDecl, llvm::GlobalValue*) (/usr/lib/llvm/15/bin/../lib64/libclang-cpp.so.15+0x27424fd)
#30 0x00007f4b67d3be9d clang::CodeGen::CodeGenModule::EmitGlobalDefinition(clang::GlobalDecl, llvm::GlobalValue*) (/usr/lib/llvm/15/bin/../lib64/libclang-cpp.so.15+0x273be9d)
#31 0x00007f4b67d3b631 clang::CodeGen::CodeGenModule::EmitTopLevelDecl(clang::Decl*) (/usr/lib/llvm/15/bin/../lib64/libclang-cpp.so.15+0x273b631)
#32 0x00007f4b67dcc4cf (/usr/lib/llvm/15/bin/../lib64/libclang-cpp.so.15+0x27cc4cf)
#33 0x00007f4b67d18d6f (/usr/lib/llvm/15/bin/../lib64/libclang-cpp.so.15+0x2718d6f)
#34 0x00007f4b66ba8de7 clang::ParseAST(clang::Sema&, bool, bool) (/usr/lib/llvm/15/bin/../lib64/libclang-cpp.so.15+0x15a8de7)
#35 0x00007f4b68617d5d clang::FrontendAction::Execute() (/usr/lib/llvm/15/bin/../lib64/libclang-cpp.so.15+0x3017d5d)
#36 0x00007f4b685939b6 clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/usr/lib/llvm/15/bin/../lib64/libclang-cpp.so.15+0x2f939b6)
#37 0x00007f4b6868dbfe clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/usr/lib/llvm/15/bin/../lib64/libclang-cpp.so.15+0x308dbfe)
#38 0x0000558fcf46cbc5 cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (/usr/lib/llvm/15/bin/clang+++0x16bc5)
#39 0x0000558fcf46aa36 (/usr/lib/llvm/15/bin/clang+++0x14a36)
#40 0x00007f4b6825ba52 (/usr/lib/llvm/15/bin/../lib64/libclang-cpp.so.15+0x2c5ba52)
#41 0x00007f4b61f6bfaf llvm::CrashRecoveryContext::RunSafely(llvm::function_ref<void ()>) (/usr/lib/llvm/15/bin/../lib64/libLLVM-15.so+0x356bfaf)
#42 0x00007f4b6825b273 clang::driver::CC1Command::Execute(llvm::ArrayRef<llvm::Optional<llvm::StringRef>>, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>*, bool*) const (/usr/lib/llvm/15/bin/../lib64/libclang-cpp.so.15+0x2c5b273)
#43 0x00007f4b68223f6a clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&, clang::driver::Command const*&, bool) const (/usr/lib/llvm/15/bin/../lib64/libclang-cpp.so.15+0x2c23f6a)
#44 0x00007f4b6822425e clang::driver::Compilation::ExecuteJobs(clang::driver::JobList const&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&, bool) const (/usr/lib/llvm/15/bin/../lib64/libclang-cpp.so.15+0x2c2425e)
#45 0x00007f4b6823e28c clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&) (/usr/lib/llvm/15/bin/../lib64/libclang-cpp.so.15+0x2c3e28c)
#46 0x0000558fcf46a114 clang_main(int, char**) (/usr/lib/llvm/15/bin/clang+++0x14114)
#47 0x00007f4b6545434a (/lib64/libc.so.6+0x2334a)
#48 0x00007f4b654543fc __libc_start_main (/lib64/libc.so.6+0x233fc)
#49 0x0000558fcf467541 _start (/usr/lib/llvm/15/bin/clang+++0x11541)
clang-15: error: clang frontend command failed with exit code 139 (use -v to see invocation)

Minimal reproducible example compiled with clang++ -std=c++20:

namespace std {
    class source_location {
    public:
        struct __impl;
        static constexpr source_location current(const __impl* __p = __builtin_source_location()) {
            source_location loc;
            loc.impl = __p;
            return loc;
        }
        [[nodiscard]] constexpr unsigned int line() const { return impl ? impl->_M_line : 0; }
        struct __impl {
            const char* _M_file_name;
            const char* _M_function_name;
            unsigned int _M_line;
            unsigned int _M_column;
        };
        const __impl* impl = nullptr;
    };
}

template<typename... Args, std::source_location loc = std::source_location::current()>
[[noreturn]] static inline void panic(Args... args) {
    while (true);
}

int main() {
    panic("Hello");
}

backtrace.txt
allocator-37f680.cpp.txt
allocator-37f680.sh.txt

[shafik]

It looks like source_location uses UnnamedGlobalConstantDecl underneath and CXXNameMangler::mangle(GlobalDecl GD) does not know how to handle that. I think this is probably a quick fix but let me dig some more.

[cor3ntin]

std::source_location has private member, which means it's not a structural type
https://godbolt.org/z/nGhc9ecEY

So the only way to reproduce the crash is to use a std::source_location object that is not conforming, which makes this bug fairly low priority (until such time std::source_location is specified to be a structural type, should that ever happen)

[erichkeane]

std::source_location has private member, which means it's not a structural type https://godbolt.org/z/nGhc9ecEY

So the only way to reproduce the crash is to use a std::source_location object that is not conforming, which makes this bug fairly low priority (until such time std::source_location is specified to be a structural type, should that ever happen)

Yeah, I don't see this as something we have any real motivation to fix either. That said, we SHOULDN'T crash, but we have no real reason to properly handle this in codegen.

IMO, the 'correct' solution here is for us to diagnose a non-standards-compliant version of std::source_location when we see it as an error. It is still low priority (again, ill-formed code is required to get this error), but would at least be a 'nice' interface to someone developing a standard library, or someone bringing in a standard library from a non-traditional source.

[shafik]

I second Eric's recommendations.