[clang] Pack indexing expressions are not mangled

[yijan4845]

This testcase is generated by a fuzzer.

Compiler Explorer: https://godbolt.org/z/EG7rrdfhb

This valid code for C++2c will crash on Clang Assertion Trunk:

template <int I, auto...V>
decltype(V...[I]) foo() {}

void fn() {
    foo<0, 0>();
}

Stack dump:

unexpected statement kind
UNREACHABLE executed at /root/llvm-project/clang/lib/AST/ItaniumMangle.cpp:4785!
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 -O3 <source>
1.	<eof> parser at end of file
2.	<source>:4:6: LLVM IR generation of declaration 'fn'
3.	<source>:4:6: Generating code for declaration 'fn'
4.	<source>:2:19: Mangling declaration 'foo'
 #0 0x0000000003ba44f8 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3ba44f8)
 #1 0x0000000003ba21bc llvm::sys::CleanupOnSignal(unsigned long) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3ba21bc)
 #2 0x0000000003aef418 CrashRecoverySignalHandler(int) CrashRecoveryContext.cpp:0:0
 #3 0x00007c9eca042520 (/lib/x86_64-linux-gnu/libc.so.6+0x42520)
 #4 0x00007c9eca0969fc pthread_kill (/lib/x86_64-linux-gnu/libc.so.6+0x969fc)
 #5 0x00007c9eca042476 gsignal (/lib/x86_64-linux-gnu/libc.so.6+0x42476)
 #6 0x00007c9eca0287f3 abort (/lib/x86_64-linux-gnu/libc.so.6+0x287f3)
 #7 0x0000000003afacea (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3afacea)
 #8 0x0000000007d47e64 (anonymous namespace)::CXXNameMangler::mangleExpression(clang::Expr const*, unsigned int, bool) ItaniumMangle.cpp:0:0
 #9 0x0000000007d39fe9 (anonymous namespace)::CXXNameMangler::mangleType(clang::QualType) ItaniumMangle.cpp:0:0
#10 0x0000000007d4d40e (anonymous namespace)::CXXNameMangler::mangleBareFunctionType(clang::FunctionProtoType const*, bool, clang::FunctionDecl const*) ItaniumMangle.cpp:0:0
#11 0x0000000007d4e561 (anonymous namespace)::CXXNameMangler::mangleFunctionEncoding(clang::GlobalDecl) ItaniumMangle.cpp:0:0
#12 0x0000000007d524ce (anonymous namespace)::ItaniumMangleContextImpl::mangleCXXName(clang::GlobalDecl, llvm::raw_ostream&) ItaniumMangle.cpp:0:0
#13 0x0000000007d774d3 clang::MangleContext::mangleName(clang::GlobalDecl, llvm::raw_ostream&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x7d774d3)
#14 0x0000000003fa8784 getMangledNameImpl(clang::CodeGen::CodeGenModule&, clang::GlobalDecl, clang::NamedDecl const*, bool) CodeGenModule.cpp:0:0
#15 0x0000000003fba35d clang::CodeGen::CodeGenModule::getMangledName(clang::GlobalDecl) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3fba35d)
#16 0x0000000003ff1541 clang::CodeGen::CodeGenModule::GetAddrOfFunction(clang::GlobalDecl, llvm::Type*, bool, bool, clang::CodeGen::ForDefinition_t) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3ff1541)
#17 0x000000000435774e clang::CodeGen::CodeGenModule::getRawFunctionPointer(clang::GlobalDecl, llvm::Type*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x435774e)
#18 0x0000000004362e34 EmitDirectCallee(clang::CodeGen::CodeGenFunction&, clang::GlobalDecl) CGExpr.cpp:0:0
#19 0x00000000043841c9 clang::CodeGen::CodeGenFunction::EmitCallee(clang::Expr const*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x43841c9)
#20 0x0000000004384177 clang::CodeGen::CodeGenFunction::EmitCallee(clang::Expr const*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4384177)
#21 0x00000000043847c3 clang::CodeGen::CodeGenFunction::EmitCallExpr(clang::CallExpr const*, clang::CodeGen::ReturnValueSlot, llvm::CallBase**) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x43847c3)
#22 0x00000000043d7f34 (anonymous namespace)::ScalarExprEmitter::VisitCallExpr(clang::CallExpr const*) CGExprScalar.cpp:0:0
#23 0x00000000043cbddb clang::StmtVisitorBase<std::add_pointer, (anonymous namespace)::ScalarExprEmitter, llvm::Value*>::Visit(clang::Stmt*) CGExprScalar.cpp:0:0
#24 0x00000000043d1a7c clang::CodeGen::CodeGenFunction::EmitScalarExpr(clang::Expr const*, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x43d1a7c)
#25 0x000000000435aabe clang::CodeGen::CodeGenFunction::EmitAnyExpr(clang::Expr const*, clang::CodeGen::AggValueSlot, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x435aabe)
#26 0x0000000004380e75 clang::CodeGen::CodeGenFunction::EmitIgnoredExpr(clang::Expr const*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4380e75)
#27 0x0000000003f06cc5 clang::CodeGen::CodeGenFunction::EmitStmt(clang::Stmt const*, llvm::ArrayRef<clang::Attr const*>) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3f06cc5)
#28 0x0000000003f0e9c4 clang::CodeGen::CodeGenFunction::EmitCompoundStmtWithoutScope(clang::CompoundStmt const&, bool, clang::CodeGen::AggValueSlot) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3f0e9c4)
#29 0x0000000003f76e64 clang::CodeGen::CodeGenFunction::EmitFunctionBody(clang::Stmt const*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3f76e64)
#30 0x0000000003f88e4c clang::CodeGen::CodeGenFunction::GenerateCode(clang::GlobalDecl, llvm::Function*, clang::CodeGen::CGFunctionInfo const&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3f88e4c)
#31 0x0000000003ff1a1a clang::CodeGen::CodeGenModule::EmitGlobalFunctionDefinition(clang::GlobalDecl, llvm::GlobalValue*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3ff1a1a)
#32 0x0000000003fec6f5 clang::CodeGen::CodeGenModule::EmitGlobalDefinition(clang::GlobalDecl, llvm::GlobalValue*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3fec6f5)
#33 0x0000000003feccab clang::CodeGen::CodeGenModule::EmitGlobal(clang::GlobalDecl) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3feccab)
#34 0x0000000003ff7153 clang::CodeGen::CodeGenModule::EmitTopLevelDecl(clang::Decl*) (.part.0) CodeGenModule.cpp:0:0
#35 0x00000000044fefe6 (anonymous namespace)::CodeGeneratorImpl::HandleTopLevelDecl(clang::DeclGroupRef) ModuleBuilder.cpp:0:0
#36 0x00000000044efbc8 clang::BackendConsumer::HandleTopLevelDecl(clang::DeclGroupRef) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x44efbc8)
#37 0x0000000006631c24 clang::ParseAST(clang::Sema&, bool, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6631c24)
#38 0x00000000044fcb58 clang::CodeGenAction::ExecuteAction() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x44fcb58)
#39 0x00000000047b6459 clang::FrontendAction::Execute() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x47b6459)
#40 0x0000000004734ffe clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4734ffe)
#41 0x000000000489bf4e clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x489bf4e)
#42 0x0000000000cda85f cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xcda85f)
#43 0x0000000000cd256a ExecuteCC1Tool(llvm::SmallVectorImpl<char const*>&, llvm::ToolContext const&) driver.cpp:0:0
#44 0x0000000004540829 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
#45 0x0000000003aef8c4 llvm::CrashRecoveryContext::RunSafely(llvm::function_ref<void ()>) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3aef8c4)
#46 0x0000000004540e1f 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
#47 0x000000000450675d clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&, clang::driver::Command const*&, bool) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x450675d)
#48 0x000000000450784d 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+++0x450784d)
#49 0x000000000450f175 clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x450f175)
#50 0x0000000000cd772f clang_main(int, char**, llvm::ToolContext const&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xcd772f)
#51 0x0000000000ba7084 main (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xba7084)
#52 0x00007c9eca029d90 (/lib/x86_64-linux-gnu/libc.so.6+0x29d90)
#53 0x00007c9eca029e40 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x29e40)
#54 0x0000000000cd201e _start (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xcd201e)
clang++: error: clang frontend command failed with exit code 134 (use -v to see invocation)
ASM generation compiler returned: 134

[llvmbot]

@llvm/issue-subscribers-clang-frontend

Author: Yihan Yang (yijan4845)

**This testcase is generated by a fuzzer.**

Compiler Explorer: https://godbolt.org/z/EG7rrdfhb

This valid code for C++2c will crash on Clang Assertion Trunk:

template <int I, auto...V>
decltype(V...[I]) foo() {}

void fn() {
    foo<0, 0>();
}

Stack dump:

unexpected statement kind
UNREACHABLE executed at /root/llvm-project/clang/lib/AST/ItaniumMangle.cpp:4785!
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 -O3 <source>
1.	<eof> parser at end of file
2.	<source>:4:6: LLVM IR generation of declaration 'fn'
3.	<source>:4:6: Generating code for declaration 'fn'
4.	<source>:2:19: Mangling declaration 'foo'
 #<!-- -->0 0x0000000003ba44f8 llvm::sys::PrintStackTrace(llvm::raw_ostream&amp;, int) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3ba44f8)
 #<!-- -->1 0x0000000003ba21bc llvm::sys::CleanupOnSignal(unsigned long) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3ba21bc)
 #<!-- -->2 0x0000000003aef418 CrashRecoverySignalHandler(int) CrashRecoveryContext.cpp:0:0
 #<!-- -->3 0x00007c9eca042520 (/lib/x86_64-linux-gnu/libc.so.6+0x42520)
 #<!-- -->4 0x00007c9eca0969fc pthread_kill (/lib/x86_64-linux-gnu/libc.so.6+0x969fc)
 #<!-- -->5 0x00007c9eca042476 gsignal (/lib/x86_64-linux-gnu/libc.so.6+0x42476)
 #<!-- -->6 0x00007c9eca0287f3 abort (/lib/x86_64-linux-gnu/libc.so.6+0x287f3)
 #<!-- -->7 0x0000000003afacea (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3afacea)
 #<!-- -->8 0x0000000007d47e64 (anonymous namespace)::CXXNameMangler::mangleExpression(clang::Expr const*, unsigned int, bool) ItaniumMangle.cpp:0:0
 #<!-- -->9 0x0000000007d39fe9 (anonymous namespace)::CXXNameMangler::mangleType(clang::QualType) ItaniumMangle.cpp:0:0
#<!-- -->10 0x0000000007d4d40e (anonymous namespace)::CXXNameMangler::mangleBareFunctionType(clang::FunctionProtoType const*, bool, clang::FunctionDecl const*) ItaniumMangle.cpp:0:0
#<!-- -->11 0x0000000007d4e561 (anonymous namespace)::CXXNameMangler::mangleFunctionEncoding(clang::GlobalDecl) ItaniumMangle.cpp:0:0
#<!-- -->12 0x0000000007d524ce (anonymous namespace)::ItaniumMangleContextImpl::mangleCXXName(clang::GlobalDecl, llvm::raw_ostream&amp;) ItaniumMangle.cpp:0:0
#<!-- -->13 0x0000000007d774d3 clang::MangleContext::mangleName(clang::GlobalDecl, llvm::raw_ostream&amp;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x7d774d3)
#<!-- -->14 0x0000000003fa8784 getMangledNameImpl(clang::CodeGen::CodeGenModule&amp;, clang::GlobalDecl, clang::NamedDecl const*, bool) CodeGenModule.cpp:0:0
#<!-- -->15 0x0000000003fba35d clang::CodeGen::CodeGenModule::getMangledName(clang::GlobalDecl) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3fba35d)
#<!-- -->16 0x0000000003ff1541 clang::CodeGen::CodeGenModule::GetAddrOfFunction(clang::GlobalDecl, llvm::Type*, bool, bool, clang::CodeGen::ForDefinition_t) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3ff1541)
#<!-- -->17 0x000000000435774e clang::CodeGen::CodeGenModule::getRawFunctionPointer(clang::GlobalDecl, llvm::Type*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x435774e)
#<!-- -->18 0x0000000004362e34 EmitDirectCallee(clang::CodeGen::CodeGenFunction&amp;, clang::GlobalDecl) CGExpr.cpp:0:0
#<!-- -->19 0x00000000043841c9 clang::CodeGen::CodeGenFunction::EmitCallee(clang::Expr const*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x43841c9)
#<!-- -->20 0x0000000004384177 clang::CodeGen::CodeGenFunction::EmitCallee(clang::Expr const*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4384177)
#<!-- -->21 0x00000000043847c3 clang::CodeGen::CodeGenFunction::EmitCallExpr(clang::CallExpr const*, clang::CodeGen::ReturnValueSlot, llvm::CallBase**) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x43847c3)
#<!-- -->22 0x00000000043d7f34 (anonymous namespace)::ScalarExprEmitter::VisitCallExpr(clang::CallExpr const*) CGExprScalar.cpp:0:0
#<!-- -->23 0x00000000043cbddb clang::StmtVisitorBase&lt;std::add_pointer, (anonymous namespace)::ScalarExprEmitter, llvm::Value*&gt;::Visit(clang::Stmt*) CGExprScalar.cpp:0:0
#<!-- -->24 0x00000000043d1a7c clang::CodeGen::CodeGenFunction::EmitScalarExpr(clang::Expr const*, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x43d1a7c)
#<!-- -->25 0x000000000435aabe clang::CodeGen::CodeGenFunction::EmitAnyExpr(clang::Expr const*, clang::CodeGen::AggValueSlot, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x435aabe)
#<!-- -->26 0x0000000004380e75 clang::CodeGen::CodeGenFunction::EmitIgnoredExpr(clang::Expr const*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4380e75)
#<!-- -->27 0x0000000003f06cc5 clang::CodeGen::CodeGenFunction::EmitStmt(clang::Stmt const*, llvm::ArrayRef&lt;clang::Attr const*&gt;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3f06cc5)
#<!-- -->28 0x0000000003f0e9c4 clang::CodeGen::CodeGenFunction::EmitCompoundStmtWithoutScope(clang::CompoundStmt const&amp;, bool, clang::CodeGen::AggValueSlot) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3f0e9c4)
#<!-- -->29 0x0000000003f76e64 clang::CodeGen::CodeGenFunction::EmitFunctionBody(clang::Stmt const*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3f76e64)
#<!-- -->30 0x0000000003f88e4c clang::CodeGen::CodeGenFunction::GenerateCode(clang::GlobalDecl, llvm::Function*, clang::CodeGen::CGFunctionInfo const&amp;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3f88e4c)
#<!-- -->31 0x0000000003ff1a1a clang::CodeGen::CodeGenModule::EmitGlobalFunctionDefinition(clang::GlobalDecl, llvm::GlobalValue*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3ff1a1a)
#<!-- -->32 0x0000000003fec6f5 clang::CodeGen::CodeGenModule::EmitGlobalDefinition(clang::GlobalDecl, llvm::GlobalValue*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3fec6f5)
#<!-- -->33 0x0000000003feccab clang::CodeGen::CodeGenModule::EmitGlobal(clang::GlobalDecl) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3feccab)
#<!-- -->34 0x0000000003ff7153 clang::CodeGen::CodeGenModule::EmitTopLevelDecl(clang::Decl*) (.part.0) CodeGenModule.cpp:0:0
#<!-- -->35 0x00000000044fefe6 (anonymous namespace)::CodeGeneratorImpl::HandleTopLevelDecl(clang::DeclGroupRef) ModuleBuilder.cpp:0:0
#<!-- -->36 0x00000000044efbc8 clang::BackendConsumer::HandleTopLevelDecl(clang::DeclGroupRef) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x44efbc8)
#<!-- -->37 0x0000000006631c24 clang::ParseAST(clang::Sema&amp;, bool, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6631c24)
#<!-- -->38 0x00000000044fcb58 clang::CodeGenAction::ExecuteAction() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x44fcb58)
#<!-- -->39 0x00000000047b6459 clang::FrontendAction::Execute() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x47b6459)
#<!-- -->40 0x0000000004734ffe clang::CompilerInstance::ExecuteAction(clang::FrontendAction&amp;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4734ffe)
#<!-- -->41 0x000000000489bf4e clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x489bf4e)
#<!-- -->42 0x0000000000cda85f cc1_main(llvm::ArrayRef&lt;char const*&gt;, char const*, void*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xcda85f)
#<!-- -->43 0x0000000000cd256a ExecuteCC1Tool(llvm::SmallVectorImpl&lt;char const*&gt;&amp;, llvm::ToolContext const&amp;) driver.cpp:0:0
#<!-- -->44 0x0000000004540829 void llvm::function_ref&lt;void ()&gt;::callback_fn&lt;clang::driver::CC1Command::Execute(llvm::ArrayRef&lt;std::optional&lt;llvm::StringRef&gt;&gt;, std::__cxx11::basic_string&lt;char, std::char_traits&lt;char&gt;, std::allocator&lt;char&gt;&gt;*, bool*) const::'lambda'()&gt;(long) Job.cpp:0:0
#<!-- -->45 0x0000000003aef8c4 llvm::CrashRecoveryContext::RunSafely(llvm::function_ref&lt;void ()&gt;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3aef8c4)
#<!-- -->46 0x0000000004540e1f clang::driver::CC1Command::Execute(llvm::ArrayRef&lt;std::optional&lt;llvm::StringRef&gt;&gt;, std::__cxx11::basic_string&lt;char, std::char_traits&lt;char&gt;, std::allocator&lt;char&gt;&gt;*, bool*) const (.part.0) Job.cpp:0:0
#<!-- -->47 0x000000000450675d clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&amp;, clang::driver::Command const*&amp;, bool) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x450675d)
#<!-- -->48 0x000000000450784d clang::driver::Compilation::ExecuteJobs(clang::driver::JobList const&amp;, llvm::SmallVectorImpl&lt;std::pair&lt;int, clang::driver::Command const*&gt;&gt;&amp;, bool) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x450784d)
#<!-- -->49 0x000000000450f175 clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&amp;, llvm::SmallVectorImpl&lt;std::pair&lt;int, clang::driver::Command const*&gt;&gt;&amp;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x450f175)
#<!-- -->50 0x0000000000cd772f clang_main(int, char**, llvm::ToolContext const&amp;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xcd772f)
#<!-- -->51 0x0000000000ba7084 main (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xba7084)
#<!-- -->52 0x00007c9eca029d90 (/lib/x86_64-linux-gnu/libc.so.6+0x29d90)
#<!-- -->53 0x00007c9eca029e40 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x29e40)
#<!-- -->54 0x0000000000cd201e _start (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xcd201e)
clang++: error: clang frontend command failed with exit code 134 (use -v to see invocation)
ASM generation compiler returned: 134

[zyn0217]

@cor3ntin We don't have rules for mangling pack indexing expressions, do we?

[zyn0217]

Aha, find it: itanium-cxx-abi/cxx-abi#175

[cor3ntin]

@AaronBallman @erichkeane @zygoloid no reply from the itanium group. Should we come up with something ourselves and/or use a vendor extension?

[erichkeane]

@rjmccall is our Itanium ABI owner, can he respond here?

I THINK what I'd prefer is that we come up with something ourselves, submit it as a patch to the Itanium ABI, and implement that.

[rjmccall]

The "Itanium group" is not a roomful of dedicated engineers twiddling their thumbs and waiting to invent manglings for whoever walks by. It's a communications channel for the engineers working on features — and congratulations, this now means you — to collaborate and try to maintain interoperation. So yes, what you should do is send a concrete proposal to the group, and we'll give feedback and try to identify problems, and if there aren't any problems we'll just accept it. Make sure you check out (and include in your proposal!) what other compilers are emitting for this construct, which fortunately is very easy now with godbolt.

[AaronBallman]

The "Itanium group" is not a roomful of dedicated engineers twiddling their thumbs and waiting to invent manglings for whoever walks by. It's a communications channel for the engineers working on features — and congratulations, this now means you — to collaborate and try to maintain interoperation. So yes, what you should do is send a concrete proposal to the group, and we'll give feedback and try to identify problems, and if there aren't any problems we'll just accept it. Make sure you check out (and include in your proposal!) what other compilers are emitting for this construct, which fortunately is very easy now with godbolt.

I think what Erich and Corentin are asking is if you could help determine what a reasonable starting point is so one of them could make a quality proposal to the Itanium group. It's not really documented anywhere in the Itanium group that people are expected to come prepared with a solution, and not everyone feels qualified to make such a proposal, and as the Clang community's Itanium ABI maintainer, you're in a good position to help out.