Clang assertion failure: "Unable to find unexpanded parameter packs"

[zmodem]

We hit this in some new code, so it may not be a Clang regression:

Preprocessed source: a.ii.gz

$ build/bin/clang -cc1 -triple x86_64-unknown-linux-gnu -fsyntax-only -std=c++20 /tmp/a.ii -w
clang: /work/llvm-project/clang/lib/Sema/SemaTemplateVariadic.cpp:456: bool clang::Sema::DiagnoseUnexpandedParameterPack(Expr *, UnexpandedParameterPackContext): Assertion `(!Unexpanded.empty() || Visitor.containsFunctionParmPackExpr()) && "Unable to find unexpanded parameter packs"' 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: build/bin/clang -cc1 -triple x86_64-unknown-linux-gnu -fsyntax-only -std=c++20 /tmp/a.ii -w
1.      <eof> parser at end of file
2.      ../../remoting/host/linux/gvariant_ref.h:709:22: instantiating function definition 'remoting::gvariant::GVariantRef<Type<20UL - 1>{{}, {"(ii{s((xt)(xt))}uv)"}}>::Destructure<int &, int &, std::tuple<std::string &, std::tuple<std::tuple<long &, unsigned long &> &&, std::tuple<long &, unsigned long &> &&> &&>, unsigned int &, std::tuple<remoting::gvariant::GVariantRef<> &>>'
 #0 0x000055cb15dfdc88 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (build/bin/clang+0x3b7fc88)
 #1 0x000055cb15dfb83e llvm::sys::RunSignalHandlers() (build/bin/clang+0x3b7d83e)
 #2 0x000055cb15dfe318 SignalHandler(int) Signals.cpp:0:0
 #3 0x00007f8570e591a0 (/lib/x86_64-linux-gnu/libc.so.6+0x3d1a0)
 #4 0x00007f8570ea70ec __pthread_kill_implementation ./nptl/pthread_kill.c:44:76
 #5 0x00007f8570e59102 gsignal ./signal/../sysdeps/posix/raise.c:27:6
 #6 0x00007f8570e424f2 abort ./stdlib/abort.c:81:7
 #7 0x00007f8570e42415 _nl_load_domain ./intl/loadmsgcat.c:1177:9
 #8 0x00007f8570e51d32 (/lib/x86_64-linux-gnu/libc.so.6+0x35d32)
 #9 0x000055cb18e057ea (build/bin/clang+0x6b877ea)
#10 0x000055cb18778d7c clang::Sema::ActOnFinishFullExpr(clang::Expr*, clang::SourceLocation, bool, bool, bool) (build/bin/clang+0x64fad7c)
#11 0x000055cb1862032a clang::Sema::ActOnCondition(clang::Scope*, clang::SourceLocation, clang::Expr*, clang::Sema::ConditionKind, bool) (build/bin/clang+0x63a232a)
#12 0x000055cb18d93221 clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformCondition(clang::SourceLocation, clang::VarDecl*, clang::Expr*, clang::Sema::ConditionKind) SemaTemplateInstantiate.cpp:0:0
#13 0x000055cb18d90126 clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformIfStmt(clang::IfStmt*) SemaTemplateInstantiate.cpp:0:0
#14 0x000055cb18d721e2 clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformCompoundStmt(clang::CompoundStmt*, bool) SemaTemplateInstantiate.cpp:0:0
#15 0x000055cb18d78b30 clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformLambdaExpr(clang::LambdaExpr*) SemaTemplateInstantiate.cpp:0:0
#16 0x000055cb18d685e8 (anonymous namespace)::TemplateInstantiator::TransformLambdaExpr(clang::LambdaExpr*) SemaTemplateInstantiate.cpp:0:0
#17 0x000055cb18d6b0f5 clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformCallExpr(clang::CallExpr*) SemaTemplateInstantiate.cpp:0:0
#18 0x000055cb18d6dcd5 clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformCXXFoldExpr(clang::CXXFoldExpr*) SemaTemplateInstantiate.cpp:0:0
#19 0x000055cb18cf7ec5 clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformStmt(clang::Stmt*, clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::StmtDiscardKind) SemaTemplateInstantiate.cpp:0:0
#20 0x000055cb18d721e2 clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformCompoundStmt(clang::CompoundStmt*, bool) SemaTemplateInstantiate.cpp:0:0
#21 0x000055cb18d78b30 clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformLambdaExpr(clang::LambdaExpr*) SemaTemplateInstantiate.cpp:0:0
#22 0x000055cb18d685e8 (anonymous namespace)::TemplateInstantiator::TransformLambdaExpr(clang::LambdaExpr*) SemaTemplateInstantiate.cpp:0:0
#23 0x000055cb18d6b0f5 clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformCallExpr(clang::CallExpr*) SemaTemplateInstantiate.cpp:0:0
#24 0x000055cb18cf7ec5 clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformStmt(clang::Stmt*, clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::StmtDiscardKind) SemaTemplateInstantiate.cpp:0:0
#25 0x000055cb18d721e2 clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformCompoundStmt(clang::CompoundStmt*, bool) SemaTemplateInstantiate.cpp:0:0
#26 0x000055cb18cf7e5a clang::Sema::SubstStmt(clang::Stmt*, clang::MultiLevelTemplateArgumentList const&) (build/bin/clang+0x6a79e5a)
#27 0x000055cb18dc1022 clang::Sema::InstantiateFunctionDefinition(clang::SourceLocation, clang::FunctionDecl*, bool, bool, bool) (build/bin/clang+0x6b43022)
#28 0x000055cb18dc40ee clang::Sema::PerformPendingInstantiations(bool) (build/bin/clang+0x6b460ee)
#29 0x000055cb182b992d clang::Sema::ActOnEndOfTranslationUnitFragment(clang::Sema::TUFragmentKind) (build/bin/clang+0x603b92d)
#30 0x000055cb182ba0ac clang::Sema::ActOnEndOfTranslationUnit() (build/bin/clang+0x603c0ac)
#31 0x000055cb18171bee clang::Parser::ParseTopLevelDecl(clang::OpaquePtr<clang::DeclGroupRef>&, clang::Sema::ModuleImportState&) (build/bin/clang+0x5ef3bee)
#32 0x000055cb1816dfee clang::ParseAST(clang::Sema&, bool, bool) (build/bin/clang+0x5eeffee)
#33 0x000055cb1685d17f clang::FrontendAction::Execute() (build/bin/clang+0x45df17f)
#34 0x000055cb167ceacd clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (build/bin/clang+0x4550acd)
#35 0x000055cb1693c747 clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (build/bin/clang+0x46be747)
#36 0x000055cb1363f56e cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (build/bin/clang+0x13c156e)
#37 0x000055cb1363bb8e ExecuteCC1Tool(llvm::SmallVectorImpl<char const*>&, llvm::ToolContext const&) driver.cpp:0:0
#38 0x000055cb1363abad clang_main(int, char**, llvm::ToolContext const&) (build/bin/clang+0x13bcbad)
#39 0x000055cb1364ace7 main (build/bin/clang+0x13ccce7)
#40 0x00007f8570e43b8a __libc_start_call_main ./csu/../sysdeps/nptl/libc_start_call_main.h:74:3
#41 0x00007f8570e43c45 call_init ./csu/../csu/libc-start.c:128:20
#42 0x00007f8570e43c45 __libc_start_main ./csu/../csu/libc-start.c:347:5
#43 0x000055cb13639761 _start (build/bin/clang+0x13bb761)
Aborted

[llvmbot]

@llvm/issue-subscribers-clang-frontend

Author: Hans (zmodem)

We hit this in some new code, so it may not be a Clang regression:

Preprocessed source: a.ii.gz

$ build/bin/clang -cc1 -triple x86_64-unknown-linux-gnu -fsyntax-only -std=c++20 /tmp/a.ii -w
clang: /work/llvm-project/clang/lib/Sema/SemaTemplateVariadic.cpp:456: bool clang::Sema::DiagnoseUnexpandedParameterPack(Expr *, UnexpandedParameterPackContext): Assertion `(!Unexpanded.empty() || Visitor.containsFunctionParmPackExpr()) && "Unable to find unexpanded parameter packs"' 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: build/bin/clang -cc1 -triple x86_64-unknown-linux-gnu -fsyntax-only -std=c++20 /tmp/a.ii -w
1.      <eof> parser at end of file
2.      ../../remoting/host/linux/gvariant_ref.h:709:22: instantiating function definition 'remoting::gvariant::GVariantRef<Type<20UL - 1>{{}, {"(ii{s((xt)(xt))}uv)"}}>::Destructure<int &, int &, std::tuple<std::string &, std::tuple<std::tuple<long &, unsigned long &> &&, std::tuple<long &, unsigned long &> &&> &&>, unsigned int &, std::tuple<remoting::gvariant::GVariantRef<> &>>'
 #<!-- -->0 0x000055cb15dfdc88 llvm::sys::PrintStackTrace(llvm::raw_ostream&amp;, int) (build/bin/clang+0x3b7fc88)
 #<!-- -->1 0x000055cb15dfb83e llvm::sys::RunSignalHandlers() (build/bin/clang+0x3b7d83e)
 #<!-- -->2 0x000055cb15dfe318 SignalHandler(int) Signals.cpp:0:0
 #<!-- -->3 0x00007f8570e591a0 (/lib/x86_64-linux-gnu/libc.so.6+0x3d1a0)
 #<!-- -->4 0x00007f8570ea70ec __pthread_kill_implementation ./nptl/pthread_kill.c:44:76
 #<!-- -->5 0x00007f8570e59102 gsignal ./signal/../sysdeps/posix/raise.c:27:6
 #<!-- -->6 0x00007f8570e424f2 abort ./stdlib/abort.c:81:7
 #<!-- -->7 0x00007f8570e42415 _nl_load_domain ./intl/loadmsgcat.c:1177:9
 #<!-- -->8 0x00007f8570e51d32 (/lib/x86_64-linux-gnu/libc.so.6+0x35d32)
 #<!-- -->9 0x000055cb18e057ea (build/bin/clang+0x6b877ea)
#<!-- -->10 0x000055cb18778d7c clang::Sema::ActOnFinishFullExpr(clang::Expr*, clang::SourceLocation, bool, bool, bool) (build/bin/clang+0x64fad7c)
#<!-- -->11 0x000055cb1862032a clang::Sema::ActOnCondition(clang::Scope*, clang::SourceLocation, clang::Expr*, clang::Sema::ConditionKind, bool) (build/bin/clang+0x63a232a)
#<!-- -->12 0x000055cb18d93221 clang::TreeTransform&lt;(anonymous namespace)::TemplateInstantiator&gt;::TransformCondition(clang::SourceLocation, clang::VarDecl*, clang::Expr*, clang::Sema::ConditionKind) SemaTemplateInstantiate.cpp:0:0
#<!-- -->13 0x000055cb18d90126 clang::TreeTransform&lt;(anonymous namespace)::TemplateInstantiator&gt;::TransformIfStmt(clang::IfStmt*) SemaTemplateInstantiate.cpp:0:0
#<!-- -->14 0x000055cb18d721e2 clang::TreeTransform&lt;(anonymous namespace)::TemplateInstantiator&gt;::TransformCompoundStmt(clang::CompoundStmt*, bool) SemaTemplateInstantiate.cpp:0:0
#<!-- -->15 0x000055cb18d78b30 clang::TreeTransform&lt;(anonymous namespace)::TemplateInstantiator&gt;::TransformLambdaExpr(clang::LambdaExpr*) SemaTemplateInstantiate.cpp:0:0
#<!-- -->16 0x000055cb18d685e8 (anonymous namespace)::TemplateInstantiator::TransformLambdaExpr(clang::LambdaExpr*) SemaTemplateInstantiate.cpp:0:0
#<!-- -->17 0x000055cb18d6b0f5 clang::TreeTransform&lt;(anonymous namespace)::TemplateInstantiator&gt;::TransformCallExpr(clang::CallExpr*) SemaTemplateInstantiate.cpp:0:0
#<!-- -->18 0x000055cb18d6dcd5 clang::TreeTransform&lt;(anonymous namespace)::TemplateInstantiator&gt;::TransformCXXFoldExpr(clang::CXXFoldExpr*) SemaTemplateInstantiate.cpp:0:0
#<!-- -->19 0x000055cb18cf7ec5 clang::TreeTransform&lt;(anonymous namespace)::TemplateInstantiator&gt;::TransformStmt(clang::Stmt*, clang::TreeTransform&lt;(anonymous namespace)::TemplateInstantiator&gt;::StmtDiscardKind) SemaTemplateInstantiate.cpp:0:0
#<!-- -->20 0x000055cb18d721e2 clang::TreeTransform&lt;(anonymous namespace)::TemplateInstantiator&gt;::TransformCompoundStmt(clang::CompoundStmt*, bool) SemaTemplateInstantiate.cpp:0:0
#<!-- -->21 0x000055cb18d78b30 clang::TreeTransform&lt;(anonymous namespace)::TemplateInstantiator&gt;::TransformLambdaExpr(clang::LambdaExpr*) SemaTemplateInstantiate.cpp:0:0
#<!-- -->22 0x000055cb18d685e8 (anonymous namespace)::TemplateInstantiator::TransformLambdaExpr(clang::LambdaExpr*) SemaTemplateInstantiate.cpp:0:0
#<!-- -->23 0x000055cb18d6b0f5 clang::TreeTransform&lt;(anonymous namespace)::TemplateInstantiator&gt;::TransformCallExpr(clang::CallExpr*) SemaTemplateInstantiate.cpp:0:0
#<!-- -->24 0x000055cb18cf7ec5 clang::TreeTransform&lt;(anonymous namespace)::TemplateInstantiator&gt;::TransformStmt(clang::Stmt*, clang::TreeTransform&lt;(anonymous namespace)::TemplateInstantiator&gt;::StmtDiscardKind) SemaTemplateInstantiate.cpp:0:0
#<!-- -->25 0x000055cb18d721e2 clang::TreeTransform&lt;(anonymous namespace)::TemplateInstantiator&gt;::TransformCompoundStmt(clang::CompoundStmt*, bool) SemaTemplateInstantiate.cpp:0:0
#<!-- -->26 0x000055cb18cf7e5a clang::Sema::SubstStmt(clang::Stmt*, clang::MultiLevelTemplateArgumentList const&amp;) (build/bin/clang+0x6a79e5a)
#<!-- -->27 0x000055cb18dc1022 clang::Sema::InstantiateFunctionDefinition(clang::SourceLocation, clang::FunctionDecl*, bool, bool, bool) (build/bin/clang+0x6b43022)
#<!-- -->28 0x000055cb18dc40ee clang::Sema::PerformPendingInstantiations(bool) (build/bin/clang+0x6b460ee)
#<!-- -->29 0x000055cb182b992d clang::Sema::ActOnEndOfTranslationUnitFragment(clang::Sema::TUFragmentKind) (build/bin/clang+0x603b92d)
#<!-- -->30 0x000055cb182ba0ac clang::Sema::ActOnEndOfTranslationUnit() (build/bin/clang+0x603c0ac)
#<!-- -->31 0x000055cb18171bee clang::Parser::ParseTopLevelDecl(clang::OpaquePtr&lt;clang::DeclGroupRef&gt;&amp;, clang::Sema::ModuleImportState&amp;) (build/bin/clang+0x5ef3bee)
#<!-- -->32 0x000055cb1816dfee clang::ParseAST(clang::Sema&amp;, bool, bool) (build/bin/clang+0x5eeffee)
#<!-- -->33 0x000055cb1685d17f clang::FrontendAction::Execute() (build/bin/clang+0x45df17f)
#<!-- -->34 0x000055cb167ceacd clang::CompilerInstance::ExecuteAction(clang::FrontendAction&amp;) (build/bin/clang+0x4550acd)
#<!-- -->35 0x000055cb1693c747 clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (build/bin/clang+0x46be747)
#<!-- -->36 0x000055cb1363f56e cc1_main(llvm::ArrayRef&lt;char const*&gt;, char const*, void*) (build/bin/clang+0x13c156e)
#<!-- -->37 0x000055cb1363bb8e ExecuteCC1Tool(llvm::SmallVectorImpl&lt;char const*&gt;&amp;, llvm::ToolContext const&amp;) driver.cpp:0:0
#<!-- -->38 0x000055cb1363abad clang_main(int, char**, llvm::ToolContext const&amp;) (build/bin/clang+0x13bcbad)
#<!-- -->39 0x000055cb1364ace7 main (build/bin/clang+0x13ccce7)
#<!-- -->40 0x00007f8570e43b8a __libc_start_call_main ./csu/../sysdeps/nptl/libc_start_call_main.h:74:3
#<!-- -->41 0x00007f8570e43c45 call_init ./csu/../csu/libc-start.c:128:20
#<!-- -->42 0x00007f8570e43c45 __libc_start_main ./csu/../csu/libc-start.c:347:5
#<!-- -->43 0x000055cb13639761 _start (build/bin/clang+0x13bb761)
Aborted

[zmodem]

creduced: a.ii.gz

[Endilll]

creduced: a.ii.gz

You can use the following arguments to prevent creduce from messing with names: --remove-pass pass_clang rename-fun --remove-pass pass_clang rename-param --remove-pass pass_clang rename-var --remove-pass pass_clang rename-class --remove-pass pass_clang rename-cxx-method --remove-pass pass_clex rename-toks

[shafik]

creduced: a.ii.gz

That is pretty smallish, so just add a godbolt link w/ the reproducer next time, thank you.

[shafik]

Looks like this goes back to clang-17: https://godbolt.org/z/dd7n7WKrr

Assertion:

clang++: /root/llvm-project/clang/lib/Sema/SemaTemplateVariadic.cpp:407:
bool clang::Sema::DiagnoseUnexpandedParameterPack(clang::Expr*, clang::Sema::UnexpandedParameterPackContext):
Assertion `!Unexpanded.empty() && "Unable to find unexpanded parameter packs"' failed.

Backtrace:

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-17.0.1/bin/clang++ -gdwarf-4 -g -o /app/output.s -mllvm --x86-asm-syntax=intel -fno-verbose-asm -S --gcc-toolchain=/opt/compiler-explorer/gcc-13.2.0 -fcolor-diagnostics -fno-crash-diagnostics --std=c++20 <source>
1.	<eof> parser at end of file
2.	<source>:102:31: instantiating function definition 'u<bw<1>{{{0, 0}}}>::bt<>'
 #0 0x00000000036e7558 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/opt/compiler-explorer/clang-assertions-17.0.1/bin/clang+++0x36e7558)
 #1 0x00000000036e53dc llvm::sys::CleanupOnSignal(unsigned long) (/opt/compiler-explorer/clang-assertions-17.0.1/bin/clang+++0x36e53dc)
 #2 0x0000000003632918 CrashRecoverySignalHandler(int) CrashRecoveryContext.cpp:0:0
 #3 0x00007ea1d7e42520 (/lib/x86_64-linux-gnu/libc.so.6+0x42520)
 #4 0x00007ea1d7e969fc pthread_kill (/lib/x86_64-linux-gnu/libc.so.6+0x969fc)
 #5 0x00007ea1d7e42476 gsignal (/lib/x86_64-linux-gnu/libc.so.6+0x42476)
 #6 0x00007ea1d7e287f3 abort (/lib/x86_64-linux-gnu/libc.so.6+0x287f3)
 #7 0x00007ea1d7e2871b (/lib/x86_64-linux-gnu/libc.so.6+0x2871b)
 #8 0x00007ea1d7e39e96 (/lib/x86_64-linux-gnu/libc.so.6+0x39e96)
 #9 0x000000000699317d (/opt/compiler-explorer/clang-assertions-17.0.1/bin/clang+++0x699317d)
#10 0x000000000614d819 clang::Sema::AddInitializerToDecl(clang::Decl*, clang::Expr*, bool) (/opt/compiler-explorer/clang-assertions-17.0.1/bin/clang+++0x614d819)
#11 0x0000000006930b67 clang::Sema::InstantiateVariableInitializer(clang::VarDecl*, clang::VarDecl*, clang::MultiLevelTemplateArgumentList const&) (/opt/compiler-explorer/clang-assertions-17.0.1/bin/clang+++0x6930b67)
#12 0x0000000006970548 clang::Sema::BuildVariableInstantiation(clang::VarDecl*, clang::VarDecl*, clang::MultiLevelTemplateArgumentList const&, llvm::SmallVector<clang::Sema::LateInstantiatedAttribute, 16u>*, clang::DeclContext*, clang::LocalInstantiationScope*, bool, clang::VarTemplateSpecializationDecl*) (/opt/compiler-explorer/clang-assertions-17.0.1/bin/clang+++0x6970548)
#13 0x0000000006979f4e clang::TemplateDeclInstantiator::VisitVarDecl(clang::VarDecl*, bool, llvm::ArrayRef<clang::BindingDecl*>*) (/opt/compiler-explorer/clang-assertions-17.0.1/bin/clang+++0x6979f4e)
#14 0x000000000697ed94 void llvm::function_ref<void ()>::callback_fn<clang::Sema::SubstDecl(clang::Decl*, clang::DeclContext*, clang::MultiLevelTemplateArgumentList const&)::'lambda'()>(long) SemaTemplateInstantiateDecl.cpp:0:0
#15 0x0000000005f3c081 clang::Sema::runWithSufficientStackSpace(clang::SourceLocation, llvm::function_ref<void ()>) (/opt/compiler-explorer/clang-assertions-17.0.1/bin/clang+++0x5f3c081)
#16 0x000000000692f46a clang::Sema::SubstDecl(clang::Decl*, clang::DeclContext*, clang::MultiLevelTemplateArgumentList const&) (/opt/compiler-explorer/clang-assertions-17.0.1/bin/clang+++0x692f46a)
#17 0x00000000068e4c1e clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformDeclStmt(clang::DeclStmt*) SemaTemplateInstantiate.cpp:0:0
#18 0x0000000006921ee8 clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformCompoundStmt(clang::CompoundStmt*, bool) SemaTemplateInstantiate.cpp:0:0
#19 0x00000000068ea31a clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformLambdaExpr(clang::LambdaExpr*) SemaTemplateInstantiate.cpp:0:0
#20 0x00000000068eae14 clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformExpr(clang::Expr*) SemaTemplateInstantiate.cpp:0:0
#21 0x00000000068f2f80 clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformCXXFoldExpr(clang::CXXFoldExpr*) SemaTemplateInstantiate.cpp:0:0
#22 0x00000000068eb089 clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformExpr(clang::Expr*) SemaTemplateInstantiate.cpp:0:0
#23 0x0000000006920ccf clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformStmt(clang::Stmt*, clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::StmtDiscardKind) SemaTemplateInstantiate.cpp:0:0
#24 0x0000000006921ee8 clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformCompoundStmt(clang::CompoundStmt*, bool) SemaTemplateInstantiate.cpp:0:0
#25 0x00000000068ea31a clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformLambdaExpr(clang::LambdaExpr*) SemaTemplateInstantiate.cpp:0:0
#26 0x00000000068eae14 clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformExpr(clang::Expr*) SemaTemplateInstantiate.cpp:0:0
#27 0x0000000006920ccf clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformStmt(clang::Stmt*, clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::StmtDiscardKind) SemaTemplateInstantiate.cpp:0:0
#28 0x0000000006921ee8 clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformCompoundStmt(clang::CompoundStmt*, bool) SemaTemplateInstantiate.cpp:0:0
#29 0x000000000692512a clang::Sema::SubstStmt(clang::Stmt*, clang::MultiLevelTemplateArgumentList const&) (/opt/compiler-explorer/clang-assertions-17.0.1/bin/clang+++0x692512a)
#30 0x00000000069740fb clang::Sema::InstantiateFunctionDefinition(clang::SourceLocation, clang::FunctionDecl*, bool, bool, bool) (/opt/compiler-explorer/clang-assertions-17.0.1/bin/clang+++0x69740fb)
#31 0x00000000069724df clang::Sema::PerformPendingInstantiations(bool) (/opt/compiler-explorer/clang-assertions-17.0.1/bin/clang+++0x69724df)
#32 0x0000000005f5f4c9 clang::Sema::ActOnEndOfTranslationUnitFragment(clang::Sema::TUFragmentKind) (.part.0) Sema.cpp:0:0
#33 0x0000000005f5fca2 clang::Sema::ActOnEndOfTranslationUnit() (/opt/compiler-explorer/clang-assertions-17.0.1/bin/clang+++0x5f5fca2)
#34 0x0000000005df75f3 clang::Parser::ParseTopLevelDecl(clang::OpaquePtr<clang::DeclGroupRef>&, clang::Sema::ModuleImportState&) (/opt/compiler-explorer/clang-assertions-17.0.1/bin/clang+++0x5df75f3)
#35 0x0000000005deb76a clang::ParseAST(clang::Sema&, bool, bool) (/opt/compiler-explorer/clang-assertions-17.0.1/bin/clang+++0x5deb76a)
#36 0x0000000004939258 clang::CodeGenAction::ExecuteAction() (/opt/compiler-explorer/clang-assertions-17.0.1/bin/clang+++0x4939258)
#37 0x00000000041a1c09 clang::FrontendAction::Execute() (/opt/compiler-explorer/clang-assertions-17.0.1/bin/clang+++0x41a1c09)
#38 0x00000000041278ce clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/opt/compiler-explorer/clang-assertions-17.0.1/bin/clang+++0x41278ce)
#39 0x0000000004281de6 clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/opt/compiler-explorer/clang-assertions-17.0.1/bin/clang+++0x4281de6)
#40 0x0000000000bc67eb cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (/opt/compiler-explorer/clang-assertions-17.0.1/bin/clang+++0xbc67eb)
#41 0x0000000000bbefaa ExecuteCC1Tool(llvm::SmallVectorImpl<char const*>&, llvm::ToolContext const&) driver.cpp:0:0
#42 0x0000000003f83419 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
#43 0x0000000003632dc4 llvm::CrashRecoveryContext::RunSafely(llvm::function_ref<void ()>) (/opt/compiler-explorer/clang-assertions-17.0.1/bin/clang+++0x3632dc4)
#44 0x0000000003f83a0f 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
#45 0x0000000003f4b275 clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&, clang::driver::Command const*&, bool) const (/opt/compiler-explorer/clang-assertions-17.0.1/bin/clang+++0x3f4b275)
#46 0x0000000003f4bcdd clang::driver::Compilation::ExecuteJobs(clang::driver::JobList const&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&, bool) const (/opt/compiler-explorer/clang-assertions-17.0.1/bin/clang+++0x3f4bcdd)
#47 0x0000000003f5385d clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&) (/opt/compiler-explorer/clang-assertions-17.0.1/bin/clang+++0x3f5385d)
#48 0x0000000000bc4a87 clang_main(int, char**, llvm::ToolContext const&) (/opt/compiler-explorer/clang-assertions-17.0.1/bin/clang+++0xbc4a87)
#49 0x0000000000abef61 main (/opt/compiler-explorer/clang-assertions-17.0.1/bin/clang+++0xabef61)
#50 0x00007ea1d7e29d90 (/lib/x86_64-linux-gnu/libc.so.6+0x29d90)
#51 0x00007ea1d7e29e40 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x29e40)
#52 0x0000000000bbea8e _start (/opt/compiler-explorer/clang-assertions-17.0.1/bin/clang+++0xbbea8e)
clang++: error: clang frontend command failed with exit code 134 (use -v to see invocation)
Compiler returned: 134

[zmodem]

Oh, I didn't realize this is a crash-on-invalid. Without asserts, Clang accepts it fine.

[zyn0217]

Are you comfortable rerunning the reduction following @Endilll 's suggestion? It's difficult for us to understand/debug the problem with these messed names. Thanks

[zmodem]

Are you comfortable rerunning the reduction following @Endilll 's suggestion? It's difficult for us to understand/debug the problem with these messed names. Thanks

Sure! Here: a.ii.gz and Godbolt for convenience: https://godbolt.org/z/5eKqPM7qr