Assertion failure: Copy constructor should not be deleted

[davidstone]

Bugzilla Link	43200
Resolution	WORKSFORME
Resolved on	Oct 29, 2021 07:04
Version	trunk
OS	Linux
CC	@AaronBallman,@zygoloid

Extended Description

The following code causes an assertion failure on clang trunk:

template <bool> struct enable_if {};
template <typename> struct types {};
template <typename LHS, typename RHS>
constexpr bool operator==(types<LHS>, types<RHS>) {
  return true;
}
template <typename T>
constexpr bool is_valid = types<T>{} == types<T &>{};
struct A {
  template <typename T, typename = typename enable_if<is_valid<T>>::type>
  A(T value);
};
struct B {
  A m_max;
};
struct C {
  B m_pp;
};
B &make_b();
bool operator==(C, C) { auto b = make_b(); }

clang-10: /home/david/llvm/clang/include/clang/AST/DeclCXX.h:1020: void clang::CXXRecordDecl::setImplicitCopyConstructorIsDeleted(): Assertion `(data().DefaultedCopyConstructorIsDeleted || needsOverloadResolutionForCopyConstructor()) && "Copy constructor should not be deleted"' failed.
Stack dump:
0. Program arguments: /home/david/llvm/build/bin/clang-10 -cc1 -triple x86_64-unknown-linux-gnu -emit-obj -mrelax-all -disable-free -main-file-name test.cpp -mrelocation-model static -mthread-model posix -mframe-pointer=all -fmath-errno -masm-verbose -mconstructor-aliases -munwind-tables -fuse-init-array -target-cpu x86-64 -dwarf-column-info -debugger-tuning=gdb -coverage-notes-file /dev/null.gcno -resource-dir /home/david/llvm/build/lib/clang/10.0.0 -internal-isystem /usr/lib/gcc/x86_64-pc-linux-gnu/9.2.0/include/g++-v9 -internal-isystem /usr/lib/gcc/x86_64-pc-linux-gnu/9.2.0/include/g++-v9/x86_64-pc-linux-gnu -internal-isystem /usr/lib/gcc/x86_64-pc-linux-gnu/9.2.0/include/g++-v9/backward -internal-isystem /usr/local/include -internal-isystem /home/david/llvm/build/lib/clang/10.0.0/include -internal-externc-isystem /include -internal-externc-isystem /usr/include -Wfatal-errors -w -std=c++17 -fdeprecated-macro -fdebug-compilation-dir /home/david/tm5/reduce -ferror-limit 19 -fmessage-length 0 -fobjc-runtime=gcc -fcxx-exceptions -fexceptions -fdiagnostics-show-option -fcolor-diagnostics -o /dev/null -x c++ test.cpp

1. test.cpp:20:42: current parser token ';'
2. test.cpp:20:23: parsing function body 'operator=='
3. test.cpp:20:23: in compound statement ('{}')
4. test.cpp:8:16: instantiating variable definition 'is_valid'
   #​0 0x000000000313ee4d PrintStackTraceSignalHandler(void*) (.llvm.14200593635904155002) (/home/david/llvm/build/bin/clang-10+0x313ee4d)
   #​1 0x000000000313c630 llvm::sys::RunSignalHandlers() (/home/david/llvm/build/bin/clang-10+0x313c630)
   #​2 0x000000000313f2e8 SignalHandler(int) (/home/david/llvm/build/bin/clang-10+0x313f2e8)
   #​3 0x00007f8f7f671660 __restore_rt (/lib64/libpthread.so.0+0x14660)
   #​4 0x00007f8f7f082d21 raise (/lib64/libc.so.6+0x38d21)
   #​5 0x00007f8f7f06c535 abort (/lib64/libc.so.6+0x22535)
   #​6 0x00007f8f7f06c40f _nl_load_domain.cold (/lib64/libc.so.6+0x2240f)
   #​7 0x00007f8f7f07a712 (/lib64/libc.so.6+0x30712)
   #​8 0x0000000004ccbf4f (/home/david/llvm/build/bin/clang-10+0x4ccbf4f)
   #​9 0x0000000004f15fc2 void llvm::function_ref<void ()>::callback_fnclang::Sema::LookupConstructors(clang::CXXRecordDecl*)::$_13(long) (/home/david/llvm/build/bin/clang-10+0x4f15fc2)
   #​10 0x0000000004efbf95 clang::Sema::LookupConstructors(clang::CXXRecordDecl*) (/home/david/llvm/build/bin/clang-10+0x4efbf95)
   #​11 0x0000000004fcd257 IsUserDefinedConversion(clang::Sema&, clang::Expr*, clang::QualType, clang::UserDefinedConversionSequence&, clang::OverloadCandidateSet&, bool, bool) (/home/david/llvm/build/bin/clang-10+0x4fcd257)
   #​12 0x0000000004ffffc0 TryUserDefinedConversion(clang::Sema&, clang::Expr*, clang::QualType, bool, bool, bool, bool, bool, bool) (/home/david/llvm/build/bin/clang-10+0x4ffffc0)
   #​13 0x0000000004fc6aff TryImplicitConversion(clang::Sema&, clang::Expr*, clang::QualType, bool, bool, bool, bool, bool, bool) (.llvm.5478737526472470733) (/home/david/llvm/build/bin/clang-10+0x4fc6aff)
   #​14 0x0000000004fd794d TryCopyInitialization(clang::Sema&, clang::Expr*, clang::QualType, bool, bool, bool, bool) (/home/david/llvm/build/bin/clang-10+0x4fd794d)
   #​15 0x0000000004fd6572 clang::Sema::AddOverloadCandidate(clang::FunctionDecl*, clang::DeclAccessPair, llvm::ArrayRefclang::Expr*, clang::OverloadCandidateSet&, bool, bool, bool, bool, clang::CallExpr::ADLCallKind, llvm::MutableArrayRefclang::ImplicitConversionSequence) (/home/david/llvm/build/bin/clang-10+0x4fd6572)
   #​16 0x0000000004fe3723 clang::Sema::AddArgumentDependentLookupCandidates(clang::DeclarationName, clang::SourceLocation, llvm::ArrayRefclang::Expr*, clang::TemplateArgumentListInfo*, clang::OverloadCandidateSet&, bool) (/home/david/llvm/build/bin/clang-10+0x4fe3723)
   #​17 0x0000000004ff343f clang::Sema::CreateOverloadedBinOp(clang::SourceLocation, clang::BinaryOperatorKind, clang::UnresolvedSetImpl const&, clang::Expr*, clang::Expr*, bool) (/home/david/llvm/build/bin/clang-10+0x4ff343f)
   #​18 0x000000000516e0c0 clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformCXXOperatorCallExpr(clang::CXXOperatorCallExpr*) (/home/david/llvm/build/bin/clang-10+0x516e0c0)
   #​19 0x00000000051ad93c clang::Sema::InstantiateVariableInitializer(clang::VarDecl*, clang::VarDecl*, clang::MultiLevelTemplateArgumentList const&) (/home/david/llvm/build/bin/clang-10+0x51ad93c)
   #​20 0x00000000051ad6ee clang::Sema::CompleteVarTemplateSpecializationDecl(clang::VarTemplateSpecializationDecl*, clang::VarDecl*, clang::MultiLevelTemplateArgumentList const&) (/home/david/llvm/build/bin/clang-10+0x51ad6ee)
   #​21 0x00000000051aee0d clang::Sema::InstantiateVariableDefinition(clang::SourceLocation, clang::VarDecl*, bool, bool, bool) (/home/david/llvm/build/bin/clang-10+0x51aee0d)
   #​22 0x0000000004dc0f3c DoMarkVarDeclReferenced(clang::Sema&, clang::SourceLocation, clang::VarDecl*, clang::Expr*) (.llvm.6274768002712316616) (/home/david/llvm/build/bin/clang-10+0x4dc0f3c)
   #​23 0x0000000004d6cb3d clang::Sema::BuildDeclRefExpr(clang::ValueDecl*, clang::QualType, clang::ExprValueKind, clang::DeclarationNameInfo const&, clang::NestedNameSpecifierLoc, clang::NamedDecl*, clang::SourceLocation, clang::TemplateArgumentListInfo const*) (/home/david/llvm/build/bin/clang-10+0x4d6cb3d)
   #​24 0x0000000004d72761 clang::Sema::BuildDeclarationNameExpr(clang::CXXScopeSpec const&, clang::DeclarationNameInfo const&, clang::NamedDecl*, clang::NamedDecl*, clang::TemplateArgumentListInfo const*, bool) (/home/david/llvm/build/bin/clang-10+0x4d72761)
   #​25 0x000000000507ab55 clang::Sema::CheckVarTemplateId(clang::CXXScopeSpec const&, clang::DeclarationNameInfo const&, clang::VarTemplateDecl*, clang::SourceLocation, clang::TemplateArgumentListInfo const*) (/home/david/llvm/build/bin/clang-10+0x507ab55)
   #​26 0x000000000517324c clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformUnresolvedLookupExpr(clang::UnresolvedLookupExpr*) (/home/david/llvm/build/bin/clang-10+0x517324c)
   #​27 0x00000000051786ec clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformTemplateArgument(clang::TemplateArgumentLoc const&, clang::TemplateArgumentLoc&, bool) (/home/david/llvm/build/bin/clang-10+0x51786ec)
   #​28 0x0000000005176e14 clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformTemplateSpecializationType(clang::TypeLocBuilder&, clang::TemplateSpecializationTypeLoc, clang::TemplateName) (/home/david/llvm/build/bin/clang-10+0x5176e14)
   #​29 0x000000000517656c clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformTSIInObjectScope(clang::TypeLoc, clang::QualType, clang::NamedDecl*, clang::CXXScopeSpec&) (/home/david/llvm/build/bin/clang-10+0x517656c)
   #​30 0x0000000005165278 clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformNestedNameSpecifierLoc(clang::NestedNameSpecifierLoc, clang::QualType, clang::NamedDecl*) (.llvm.209458239465659423) (/home/david/llvm/build/bin/clang-10+0x5165278)
   #​31 0x000000000517d8af clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformDependentNameType(clang::TypeLocBuilder&, clang::DependentNameTypeLoc, bool) (/home/david/llvm/build/bin/clang-10+0x517d8af)
   #​32 0x000000000514ff48 clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformType(clang::TypeSourceInfo*) (.llvm.209458239465659423) (/home/david/llvm/build/bin/clang-10+0x514ff48)
   #​33 0x000000000507d989 SubstDefaultTemplateArgument(clang::Sema&, clang::TemplateDecl*, clang::SourceLocation, clang::SourceLocation, clang::TemplateTypeParmDecl*, llvm::SmallVectorImplclang::TemplateArgument&) (/home/david/llvm/build/bin/clang-10+0x507d989)
   #​34 0x000000000507d446 clang::Sema::SubstDefaultTemplateArgumentIfAvailable(clang::TemplateDecl*, clang::SourceLocation, clang::SourceLocation, clang::Decl*, llvm::SmallVectorImplclang::TemplateArgument&, bool&) (/home/david/llvm/build/bin/clang-10+0x507d446)
   #​35 0x000000000510b957 clang::Sema::FinishTemplateArgumentDeduction(clang::FunctionTemplateDecl*, llvm::SmallVectorImplclang::DeducedTemplateArgument&, unsigned int, clang::FunctionDecl*&, clang::sema::TemplateDeductionInfo&, llvm::SmallVectorImplclang::Sema::OriginalCallArg const*, bool, llvm::function_ref<bool ()>) (/home/david/llvm/build/bin/clang-10+0x510b957)
   #​36 0x000000000510dcc1 clang::Sema::DeduceTemplateArguments(clang::FunctionTemplateDecl*, clang::TemplateArgumentListInfo*, llvm::ArrayRefclang::Expr*, clang::FunctionDecl*&, clang::sema::TemplateDeductionInfo&, bool, llvm::function_ref<bool (llvm::ArrayRefclang::QualType)>) (/home/david/llvm/build/bin/clang-10+0x510dcc1)
   #​37 0x0000000004fdaff7 clang::Sema::AddTemplateOverloadCandidate(clang::FunctionTemplateDecl*, clang::DeclAccessPair, clang::TemplateArgumentListInfo*, llvm::ArrayRefclang::Expr*, clang::OverloadCandidateSet&, bool, bool, bool, clang::CallExpr::ADLCallKind) (/home/david/llvm/build/bin/clang-10+0x4fdaff7)
   #​38 0x0000000004efb845 clang::Sema::LookupSpecialMember(clang::CXXRecordDecl*, clang::Sema::CXXSpecialMember, bool, bool, bool, bool, bool) (/home/david/llvm/build/bin/clang-10+0x4efb845)
   #​39 0x0000000004cc5944 defaultedSpecialMemberIsConstexpr(clang::Sema&, clang::CXXRecordDecl*, clang::Sema::CXXSpecialMember, bool, clang::CXXConstructorDecl*, clang::Sema::InheritedConstructorInfo*) (/home/david/llvm/build/bin/clang-10+0x4cc5944)
   #​40 0x0000000004ccb81b clang::Sema::DeclareImplicitCopyConstructor(clang::CXXRecordDecl*) (/home/david/llvm/build/bin/clang-10+0x4ccb81b)
   #​41 0x0000000004f15fc2 void llvm::function_ref<void ()>::callback_fnclang::Sema::LookupConstructors(clang::CXXRecordDecl*)::$_13(long) (/home/david/llvm/build/bin/clang-10+0x4f15fc2)
   #​42 0x0000000004efbf95 clang::Sema::LookupConstructors(clang::CXXRecordDecl*) (/home/david/llvm/build/bin/clang-10+0x4efbf95)
   #​43 0x0000000004eb4656 TryConstructorInitialization(clang::Sema&, clang::InitializedEntity const&, clang::InitializationKind const&, llvm::MutableArrayRefclang::Expr*, clang::QualType, clang::QualType, clang::InitializationSequence&, bool, bool) (/home/david/llvm/build/bin/clang-10+0x4eb4656)
   #​44 0x0000000004eb0c3c clang::InitializationSequence::InitializeFrom(clang::Sema&, clang::InitializedEntity const&, clang::InitializationKind const&, llvm::MutableArrayRefclang::Expr*, bool, bool) (/home/david/llvm/build/bin/clang-10+0x4eb0c3c)
   #​45 0x0000000004bd3924 clang::Sema::AddInitializerToDecl(clang::Decl*, clang::Expr*, bool) (/home/david/llvm/build/bin/clang-10+0x4bd3924)
   #​46 0x00000000049b5d75 clang::Parser::ParseDeclarationAfterDeclaratorAndAttributes(clang::Declarator&, clang::Parser::ParsedTemplateInfo const&, clang::Parser::ForRangeInit*) (/home/david/llvm/build/bin/clang-10+0x49b5d75)
   #​47 0x00000000049b3b93 clang::Parser::ParseDeclGroup(clang::ParsingDeclSpec&, clang::DeclaratorContext, clang::SourceLocation*, clang::Parser::ForRangeInit*) (/home/david/llvm/build/bin/clang-10+0x49b3b93)
   #​48 0x00000000049add95 clang::Parser::ParseSimpleDeclaration(clang::DeclaratorContext, clang::SourceLocation&, clang::Parser::ParsedAttributesWithRange&, bool, clang::Parser::ForRangeInit*, clang::SourceLocation*) (/home/david/llvm/build/bin/clang-10+0x49add95)
   #​49 0x00000000049ad414 clang::Parser::ParseDeclaration(clang::DeclaratorContext, clang::SourceLocation&, clang::Parser::ParsedAttributesWithRange&, clang::SourceLocation*) (/home/david/llvm/build/bin/clang-10+0x49ad414)
   #​50 0x00000000049831d1 clang::Parser::ParseStatementOrDeclarationAfterAttributes(llvm::SmallVector<clang::Stmt*, 32u>&, clang::Parser::ParsedStmtContext, clang::SourceLocation*, clang::Parser::ParsedAttributesWithRange&) (/home/david/llvm/build/bin/clang-10+0x49831d1)
   #​51 0x0000000004982abb clang::Parser::ParseStatementOrDeclaration(llvm::SmallVector<clang::Stmt*, 32u>&, clang::Parser::ParsedStmtContext, clang::SourceLocation*) (/home/david/llvm/build/bin/clang-10+0x4982abb)
   #​52 0x000000000498c84e clang::Parser::ParseCompoundStatementBody(bool) (/home/david/llvm/build/bin/clang-10+0x498c84e)
   #​53 0x000000000498d8a2 clang::Parser::ParseFunctionStatementBody(clang::Decl*, clang::Parser::ParseScope&) (/home/david/llvm/build/bin/clang-10+0x498d8a2)
   #​54 0x000000000496a8cb clang::Parser::ParseFunctionDefinition(clang::ParsingDeclarator&, clang::Parser::ParsedTemplateInfo const&, clang::Parser::LateParsedAttrList*) (/home/david/llvm/build/bin/clang-10+0x496a8cb)
   #​55 0x00000000049b3a06 clang::Parser::ParseDeclGroup(clang::ParsingDeclSpec&, clang::DeclaratorContext, clang::SourceLocation*, clang::Parser::ForRangeInit*) (/home/david/llvm/build/bin/clang-10+0x49b3a06)
   #​56 0x000000000496965c clang::Parser::ParseDeclOrFunctionDefInternal(clang::Parser::ParsedAttributesWithRange&, clang::ParsingDeclSpec&, clang::AccessSpecifier) (/home/david/llvm/build/bin/clang-10+0x496965c)
   #​57 0x0000000004968f4f clang::Parser::ParseDeclarationOrFunctionDefinition(clang::Parser::ParsedAttributesWithRange&, clang::ParsingDeclSpec*, clang::AccessSpecifier) (/home/david/llvm/build/bin/clang-10+0x4968f4f)
   #​58 0x0000000004967d79 clang::Parser::ParseExternalDeclaration(clang::Parser::ParsedAttributesWithRange&, clang::ParsingDeclSpec*) (/home/david/llvm/build/bin/clang-10+0x4967d79)
   #​59 0x0000000004965a7d clang::Parser::ParseTopLevelDecl(clang::OpaquePtrclang::DeclGroupRef&, bool) (/home/david/llvm/build/bin/clang-10+0x4965a7d)
   #​60 0x0000000004960fb4 clang::ParseAST(clang::Sema&, bool, bool) (/home/david/llvm/build/bin/clang-10+0x4960fb4)
   #​61 0x0000000003ab7c1f clang::FrontendAction::Execute() (/home/david/llvm/build/bin/clang-10+0x3ab7c1f)
   #​62 0x0000000003a154d8 clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/home/david/llvm/build/bin/clang-10+0x3a154d8)
   #​63 0x0000000003b64067 clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/home/david/llvm/build/bin/clang-10+0x3b64067)
   #​64 0x000000000201134f cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (/home/david/llvm/build/bin/clang-10+0x201134f)
   #​65 0x000000000200f048 main (/home/david/llvm/build/bin/clang-10+0x200f048)
   #​66 0x00007f8f7f06df1b __libc_start_main (/lib64/libc.so.6+0x23f1b)
   #​67 0x000000000200c02a _start (/home/david/llvm/build/bin/clang-10+0x200c02a)
   clang-10: fatal error: unable to execute command: Aborted (core dumped)
   clang version 10.0.0 (https://github.com/llvm-project/llvm-project-20170507/ ca24486)
   Target: x86_64-unknown-linux-gnu
   Thread model: posix
   InstalledDir: /home/david/llvm/build/bin

[AaronBallman]

I cannot reproduce this issue with Clang. If you're still seeing the problem with Clang trunk, please reopen this bug with additional details on how to reproduce.

[shafik]

Reopening b/c this does reproduce but requires an assertions build: https://godbolt.org/z/d7n9b1oEG

[llvmbot]

@llvm/issue-subscribers-clang-frontend

Author: David Stone (davidstone)

| | | | --- | --- | | Bugzilla Link | [43200](https://llvm.org/bz43200) | | Resolution | WORKSFORME | | Resolved on | Oct 29, 2021 07:04 | | Version | trunk | | OS | Linux | | CC | @AaronBallman,@zygoloid |

Extended Description

The following code causes an assertion failure on clang trunk:

template <bool> struct enable_if {};
template <typename> struct types {};
template <typename LHS, typename RHS>
constexpr bool operator==(types<LHS>, types<RHS>) {
  return true;
}
template <typename T>
constexpr bool is_valid = types<T>{} == types<T &>{};
struct A {
  template <typename T, typename = typename enable_if<is_valid<T>>::type>
  A(T value);
};
struct B {
  A m_max;
};
struct C {
  B m_pp;
};
B &make_b();
bool operator==(C, C) { auto b = make_b(); }

clang-10: /home/david/llvm/clang/include/clang/AST/DeclCXX.h:1020: void clang::CXXRecordDecl::setImplicitCopyConstructorIsDeleted(): Assertion `(data().DefaultedCopyConstructorIsDeleted || needsOverloadResolutionForCopyConstructor()) && "Copy constructor should not be deleted"' failed.
Stack dump:
0. Program arguments: /home/david/llvm/build/bin/clang-10 -cc1 -triple x86_64-unknown-linux-gnu -emit-obj -mrelax-all -disable-free -main-file-name test.cpp -mrelocation-model static -mthread-model posix -mframe-pointer=all -fmath-errno -masm-verbose -mconstructor-aliases -munwind-tables -fuse-init-array -target-cpu x86-64 -dwarf-column-info -debugger-tuning=gdb -coverage-notes-file /dev/null.gcno -resource-dir /home/david/llvm/build/lib/clang/10.0.0 -internal-isystem /usr/lib/gcc/x86_64-pc-linux-gnu/9.2.0/include/g++-v9 -internal-isystem /usr/lib/gcc/x86_64-pc-linux-gnu/9.2.0/include/g++-v9/x86_64-pc-linux-gnu -internal-isystem /usr/lib/gcc/x86_64-pc-linux-gnu/9.2.0/include/g++-v9/backward -internal-isystem /usr/local/include -internal-isystem /home/david/llvm/build/lib/clang/10.0.0/include -internal-externc-isystem /include -internal-externc-isystem /usr/include -Wfatal-errors -w -std=c++17 -fdeprecated-macro -fdebug-compilation-dir /home/david/tm5/reduce -ferror-limit 19 -fmessage-length 0 -fobjc-runtime=gcc -fcxx-exceptions -fexceptions -fdiagnostics-show-option -fcolor-diagnostics -o /dev/null -x c++ test.cpp

1. test.cpp:20:42: current parser token ';'
2. test.cpp:20:23: parsing function body 'operator=='
3. test.cpp:20:23: in compound statement ('{}')
4. test.cpp:8:16: instantiating variable definition 'is_valid<A>'
   #&#8203;0 0x000000000313ee4d PrintStackTraceSignalHandler(void*) (.llvm.14200593635904155002) (/home/david/llvm/build/bin/clang-10+0x313ee4d)
   #&#8203;1 0x000000000313c630 llvm::sys::RunSignalHandlers() (/home/david/llvm/build/bin/clang-10+0x313c630)
   #&#8203;2 0x000000000313f2e8 SignalHandler(int) (/home/david/llvm/build/bin/clang-10+0x313f2e8)
   #&#8203;3 0x00007f8f7f671660 __restore_rt (/lib64/libpthread.so.0+0x14660)
   #&#8203;4 0x00007f8f7f082d21 raise (/lib64/libc.so.6+0x38d21)
   #&#8203;5 0x00007f8f7f06c535 abort (/lib64/libc.so.6+0x22535)
   #&#8203;6 0x00007f8f7f06c40f _nl_load_domain.cold (/lib64/libc.so.6+0x2240f)
   #&#8203;7 0x00007f8f7f07a712 (/lib64/libc.so.6+0x30712)
   #&#8203;8 0x0000000004ccbf4f (/home/david/llvm/build/bin/clang-10+0x4ccbf4f)
   #&#8203;9 0x0000000004f15fc2 void llvm::function_ref<void ()>::callback_fn<clang::Sema::LookupConstructors(clang::CXXRecordDecl*)::$_13>(long) (/home/david/llvm/build/bin/clang-10+0x4f15fc2)
   #&#8203;10 0x0000000004efbf95 clang::Sema::LookupConstructors(clang::CXXRecordDecl*) (/home/david/llvm/build/bin/clang-10+0x4efbf95)
   #&#8203;11 0x0000000004fcd257 IsUserDefinedConversion(clang::Sema&, clang::Expr*, clang::QualType, clang::UserDefinedConversionSequence&, clang::OverloadCandidateSet&, bool, bool) (/home/david/llvm/build/bin/clang-10+0x4fcd257)
   #&#8203;12 0x0000000004ffffc0 TryUserDefinedConversion(clang::Sema&, clang::Expr*, clang::QualType, bool, bool, bool, bool, bool, bool) (/home/david/llvm/build/bin/clang-10+0x4ffffc0)
   #&#8203;13 0x0000000004fc6aff TryImplicitConversion(clang::Sema&, clang::Expr*, clang::QualType, bool, bool, bool, bool, bool, bool) (.llvm.5478737526472470733) (/home/david/llvm/build/bin/clang-10+0x4fc6aff)
   #&#8203;14 0x0000000004fd794d TryCopyInitialization(clang::Sema&, clang::Expr*, clang::QualType, bool, bool, bool, bool) (/home/david/llvm/build/bin/clang-10+0x4fd794d)
   #&#8203;15 0x0000000004fd6572 clang::Sema::AddOverloadCandidate(clang::FunctionDecl*, clang::DeclAccessPair, llvm::ArrayRef<clang::Expr*>, clang::OverloadCandidateSet&, bool, bool, bool, bool, clang::CallExpr::ADLCallKind, llvm::MutableArrayRef<clang::ImplicitConversionSequence>) (/home/david/llvm/build/bin/clang-10+0x4fd6572)
   #&#8203;16 0x0000000004fe3723 clang::Sema::AddArgumentDependentLookupCandidates(clang::DeclarationName, clang::SourceLocation, llvm::ArrayRef<clang::Expr*>, clang::TemplateArgumentListInfo*, clang::OverloadCandidateSet&, bool) (/home/david/llvm/build/bin/clang-10+0x4fe3723)
   #&#8203;17 0x0000000004ff343f clang::Sema::CreateOverloadedBinOp(clang::SourceLocation, clang::BinaryOperatorKind, clang::UnresolvedSetImpl const&, clang::Expr*, clang::Expr*, bool) (/home/david/llvm/build/bin/clang-10+0x4ff343f)
   #&#8203;18 0x000000000516e0c0 clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformCXXOperatorCallExpr(clang::CXXOperatorCallExpr*) (/home/david/llvm/build/bin/clang-10+0x516e0c0)
   #&#8203;19 0x00000000051ad93c clang::Sema::InstantiateVariableInitializer(clang::VarDecl*, clang::VarDecl*, clang::MultiLevelTemplateArgumentList const&) (/home/david/llvm/build/bin/clang-10+0x51ad93c)
   #&#8203;20 0x00000000051ad6ee clang::Sema::CompleteVarTemplateSpecializationDecl(clang::VarTemplateSpecializationDecl*, clang::VarDecl*, clang::MultiLevelTemplateArgumentList const&) (/home/david/llvm/build/bin/clang-10+0x51ad6ee)
   #&#8203;21 0x00000000051aee0d clang::Sema::InstantiateVariableDefinition(clang::SourceLocation, clang::VarDecl*, bool, bool, bool) (/home/david/llvm/build/bin/clang-10+0x51aee0d)
   #&#8203;22 0x0000000004dc0f3c DoMarkVarDeclReferenced(clang::Sema&, clang::SourceLocation, clang::VarDecl*, clang::Expr*) (.llvm.6274768002712316616) (/home/david/llvm/build/bin/clang-10+0x4dc0f3c)
   #&#8203;23 0x0000000004d6cb3d clang::Sema::BuildDeclRefExpr(clang::ValueDecl*, clang::QualType, clang::ExprValueKind, clang::DeclarationNameInfo const&, clang::NestedNameSpecifierLoc, clang::NamedDecl*, clang::SourceLocation, clang::TemplateArgumentListInfo const*) (/home/david/llvm/build/bin/clang-10+0x4d6cb3d)
   #&#8203;24 0x0000000004d72761 clang::Sema::BuildDeclarationNameExpr(clang::CXXScopeSpec const&, clang::DeclarationNameInfo const&, clang::NamedDecl*, clang::NamedDecl*, clang::TemplateArgumentListInfo const*, bool) (/home/david/llvm/build/bin/clang-10+0x4d72761)
   #&#8203;25 0x000000000507ab55 clang::Sema::CheckVarTemplateId(clang::CXXScopeSpec const&, clang::DeclarationNameInfo const&, clang::VarTemplateDecl*, clang::SourceLocation, clang::TemplateArgumentListInfo const*) (/home/david/llvm/build/bin/clang-10+0x507ab55)
   #&#8203;26 0x000000000517324c clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformUnresolvedLookupExpr(clang::UnresolvedLookupExpr*) (/home/david/llvm/build/bin/clang-10+0x517324c)
   #&#8203;27 0x00000000051786ec clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformTemplateArgument(clang::TemplateArgumentLoc const&, clang::TemplateArgumentLoc&, bool) (/home/david/llvm/build/bin/clang-10+0x51786ec)
   #&#8203;28 0x0000000005176e14 clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformTemplateSpecializationType(clang::TypeLocBuilder&, clang::TemplateSpecializationTypeLoc, clang::TemplateName) (/home/david/llvm/build/bin/clang-10+0x5176e14)
   #&#8203;29 0x000000000517656c clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformTSIInObjectScope(clang::TypeLoc, clang::QualType, clang::NamedDecl*, clang::CXXScopeSpec&) (/home/david/llvm/build/bin/clang-10+0x517656c)
   #&#8203;30 0x0000000005165278 clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformNestedNameSpecifierLoc(clang::NestedNameSpecifierLoc, clang::QualType, clang::NamedDecl*) (.llvm.209458239465659423) (/home/david/llvm/build/bin/clang-10+0x5165278)
   #&#8203;31 0x000000000517d8af clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformDependentNameType(clang::TypeLocBuilder&, clang::DependentNameTypeLoc, bool) (/home/david/llvm/build/bin/clang-10+0x517d8af)
   #&#8203;32 0x000000000514ff48 clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformType(clang::TypeSourceInfo*) (.llvm.209458239465659423) (/home/david/llvm/build/bin/clang-10+0x514ff48)
   #&#8203;33 0x000000000507d989 SubstDefaultTemplateArgument(clang::Sema&, clang::TemplateDecl*, clang::SourceLocation, clang::SourceLocation, clang::TemplateTypeParmDecl*, llvm::SmallVectorImpl<clang::TemplateArgument>&) (/home/david/llvm/build/bin/clang-10+0x507d989)
   #&#8203;34 0x000000000507d446 clang::Sema::SubstDefaultTemplateArgumentIfAvailable(clang::TemplateDecl*, clang::SourceLocation, clang::SourceLocation, clang::Decl*, llvm::SmallVectorImpl<clang::TemplateArgument>&, bool&) (/home/david/llvm/build/bin/clang-10+0x507d446)
   #&#8203;35 0x000000000510b957 clang::Sema::FinishTemplateArgumentDeduction(clang::FunctionTemplateDecl*, llvm::SmallVectorImpl<clang::DeducedTemplateArgument>&, unsigned int, clang::FunctionDecl*&, clang::sema::TemplateDeductionInfo&, llvm::SmallVectorImpl<clang::Sema::OriginalCallArg> const*, bool, llvm::function_ref<bool ()>) (/home/david/llvm/build/bin/clang-10+0x510b957)
   #&#8203;36 0x000000000510dcc1 clang::Sema::DeduceTemplateArguments(clang::FunctionTemplateDecl*, clang::TemplateArgumentListInfo*, llvm::ArrayRef<clang::Expr*>, clang::FunctionDecl*&, clang::sema::TemplateDeductionInfo&, bool, llvm::function_ref<bool (llvm::ArrayRef<clang::QualType>)>) (/home/david/llvm/build/bin/clang-10+0x510dcc1)
   #&#8203;37 0x0000000004fdaff7 clang::Sema::AddTemplateOverloadCandidate(clang::FunctionTemplateDecl*, clang::DeclAccessPair, clang::TemplateArgumentListInfo*, llvm::ArrayRef<clang::Expr*>, clang::OverloadCandidateSet&, bool, bool, bool, clang::CallExpr::ADLCallKind) (/home/david/llvm/build/bin/clang-10+0x4fdaff7)
   #&#8203;38 0x0000000004efb845 clang::Sema::LookupSpecialMember(clang::CXXRecordDecl*, clang::Sema::CXXSpecialMember, bool, bool, bool, bool, bool) (/home/david/llvm/build/bin/clang-10+0x4efb845)
   #&#8203;39 0x0000000004cc5944 defaultedSpecialMemberIsConstexpr(clang::Sema&, clang::CXXRecordDecl*, clang::Sema::CXXSpecialMember, bool, clang::CXXConstructorDecl*, clang::Sema::InheritedConstructorInfo*) (/home/david/llvm/build/bin/clang-10+0x4cc5944)
   #&#8203;40 0x0000000004ccb81b clang::Sema::DeclareImplicitCopyConstructor(clang::CXXRecordDecl*) (/home/david/llvm/build/bin/clang-10+0x4ccb81b)
   #&#8203;41 0x0000000004f15fc2 void llvm::function_ref<void ()>::callback_fn<clang::Sema::LookupConstructors(clang::CXXRecordDecl*)::$_13>(long) (/home/david/llvm/build/bin/clang-10+0x4f15fc2)
   #&#8203;42 0x0000000004efbf95 clang::Sema::LookupConstructors(clang::CXXRecordDecl*) (/home/david/llvm/build/bin/clang-10+0x4efbf95)
   #&#8203;43 0x0000000004eb4656 TryConstructorInitialization(clang::Sema&, clang::InitializedEntity const&, clang::InitializationKind const&, llvm::MutableArrayRef<clang::Expr*>, clang::QualType, clang::QualType, clang::InitializationSequence&, bool, bool) (/home/david/llvm/build/bin/clang-10+0x4eb4656)
   #&#8203;44 0x0000000004eb0c3c clang::InitializationSequence::InitializeFrom(clang::Sema&, clang::InitializedEntity const&, clang::InitializationKind const&, llvm::MutableArrayRef<clang::Expr*>, bool, bool) (/home/david/llvm/build/bin/clang-10+0x4eb0c3c)
   #&#8203;45 0x0000000004bd3924 clang::Sema::AddInitializerToDecl(clang::Decl*, clang::Expr*, bool) (/home/david/llvm/build/bin/clang-10+0x4bd3924)
   #&#8203;46 0x00000000049b5d75 clang::Parser::ParseDeclarationAfterDeclaratorAndAttributes(clang::Declarator&, clang::Parser::ParsedTemplateInfo const&, clang::Parser::ForRangeInit*) (/home/david/llvm/build/bin/clang-10+0x49b5d75)
   #&#8203;47 0x00000000049b3b93 clang::Parser::ParseDeclGroup(clang::ParsingDeclSpec&, clang::DeclaratorContext, clang::SourceLocation*, clang::Parser::ForRangeInit*) (/home/david/llvm/build/bin/clang-10+0x49b3b93)
   #&#8203;48 0x00000000049add95 clang::Parser::ParseSimpleDeclaration(clang::DeclaratorContext, clang::SourceLocation&, clang::Parser::ParsedAttributesWithRange&, bool, clang::Parser::ForRangeInit*, clang::SourceLocation*) (/home/david/llvm/build/bin/clang-10+0x49add95)
   #&#8203;49 0x00000000049ad414 clang::Parser::ParseDeclaration(clang::DeclaratorContext, clang::SourceLocation&, clang::Parser::ParsedAttributesWithRange&, clang::SourceLocation*) (/home/david/llvm/build/bin/clang-10+0x49ad414)
   #&#8203;50 0x00000000049831d1 clang::Parser::ParseStatementOrDeclarationAfterAttributes(llvm::SmallVector<clang::Stmt*, 32u>&, clang::Parser::ParsedStmtContext, clang::SourceLocation*, clang::Parser::ParsedAttributesWithRange&) (/home/david/llvm/build/bin/clang-10+0x49831d1)
   #&#8203;51 0x0000000004982abb clang::Parser::ParseStatementOrDeclaration(llvm::SmallVector<clang::Stmt*, 32u>&, clang::Parser::ParsedStmtContext, clang::SourceLocation*) (/home/david/llvm/build/bin/clang-10+0x4982abb)
   #&#8203;52 0x000000000498c84e clang::Parser::ParseCompoundStatementBody(bool) (/home/david/llvm/build/bin/clang-10+0x498c84e)
   #&#8203;53 0x000000000498d8a2 clang::Parser::ParseFunctionStatementBody(clang::Decl*, clang::Parser::ParseScope&) (/home/david/llvm/build/bin/clang-10+0x498d8a2)
   #&#8203;54 0x000000000496a8cb clang::Parser::ParseFunctionDefinition(clang::ParsingDeclarator&, clang::Parser::ParsedTemplateInfo const&, clang::Parser::LateParsedAttrList*) (/home/david/llvm/build/bin/clang-10+0x496a8cb)
   #&#8203;55 0x00000000049b3a06 clang::Parser::ParseDeclGroup(clang::ParsingDeclSpec&, clang::DeclaratorContext, clang::SourceLocation*, clang::Parser::ForRangeInit*) (/home/david/llvm/build/bin/clang-10+0x49b3a06)
   #&#8203;56 0x000000000496965c clang::Parser::ParseDeclOrFunctionDefInternal(clang::Parser::ParsedAttributesWithRange&, clang::ParsingDeclSpec&, clang::AccessSpecifier) (/home/david/llvm/build/bin/clang-10+0x496965c)
   #&#8203;57 0x0000000004968f4f clang::Parser::ParseDeclarationOrFunctionDefinition(clang::Parser::ParsedAttributesWithRange&, clang::ParsingDeclSpec*, clang::AccessSpecifier) (/home/david/llvm/build/bin/clang-10+0x4968f4f)
   #&#8203;58 0x0000000004967d79 clang::Parser::ParseExternalDeclaration(clang::Parser::ParsedAttributesWithRange&, clang::ParsingDeclSpec*) (/home/david/llvm/build/bin/clang-10+0x4967d79)
   #&#8203;59 0x0000000004965a7d clang::Parser::ParseTopLevelDecl(clang::OpaquePtr<clang::DeclGroupRef>&, bool) (/home/david/llvm/build/bin/clang-10+0x4965a7d)
   #&#8203;60 0x0000000004960fb4 clang::ParseAST(clang::Sema&, bool, bool) (/home/david/llvm/build/bin/clang-10+0x4960fb4)
   #&#8203;61 0x0000000003ab7c1f clang::FrontendAction::Execute() (/home/david/llvm/build/bin/clang-10+0x3ab7c1f)
   #&#8203;62 0x0000000003a154d8 clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/home/david/llvm/build/bin/clang-10+0x3a154d8)
   #&#8203;63 0x0000000003b64067 clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/home/david/llvm/build/bin/clang-10+0x3b64067)
   #&#8203;64 0x000000000201134f cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (/home/david/llvm/build/bin/clang-10+0x201134f)
   #&#8203;65 0x000000000200f048 main (/home/david/llvm/build/bin/clang-10+0x200f048)
   #&#8203;66 0x00007f8f7f06df1b __libc_start_main (/lib64/libc.so.6+0x23f1b)
   #&#8203;67 0x000000000200c02a _start (/home/david/llvm/build/bin/clang-10+0x200c02a)
   clang-10: fatal error: unable to execute command: Aborted (core dumped)
   clang version 10.0.0 (https://github.com/llvm-project/llvm-project-20170507/ ca24486)
   Target: x86_64-unknown-linux-gnu
   Thread model: posix
   InstalledDir: /home/david/llvm/build/bin

[llvmbot]

@llvm/issue-subscribers-c-1

Author: David Stone (davidstone)

| | | | --- | --- | | Bugzilla Link | [43200](https://llvm.org/bz43200) | | Resolution | WORKSFORME | | Resolved on | Oct 29, 2021 07:04 | | Version | trunk | | OS | Linux | | CC | @AaronBallman,@zygoloid |

Extended Description

The following code causes an assertion failure on clang trunk:

template <bool> struct enable_if {};
template <typename> struct types {};
template <typename LHS, typename RHS>
constexpr bool operator==(types<LHS>, types<RHS>) {
  return true;
}
template <typename T>
constexpr bool is_valid = types<T>{} == types<T &>{};
struct A {
  template <typename T, typename = typename enable_if<is_valid<T>>::type>
  A(T value);
};
struct B {
  A m_max;
};
struct C {
  B m_pp;
};
B &make_b();
bool operator==(C, C) { auto b = make_b(); }

clang-10: /home/david/llvm/clang/include/clang/AST/DeclCXX.h:1020: void clang::CXXRecordDecl::setImplicitCopyConstructorIsDeleted(): Assertion `(data().DefaultedCopyConstructorIsDeleted || needsOverloadResolutionForCopyConstructor()) && "Copy constructor should not be deleted"' failed.
Stack dump:
0. Program arguments: /home/david/llvm/build/bin/clang-10 -cc1 -triple x86_64-unknown-linux-gnu -emit-obj -mrelax-all -disable-free -main-file-name test.cpp -mrelocation-model static -mthread-model posix -mframe-pointer=all -fmath-errno -masm-verbose -mconstructor-aliases -munwind-tables -fuse-init-array -target-cpu x86-64 -dwarf-column-info -debugger-tuning=gdb -coverage-notes-file /dev/null.gcno -resource-dir /home/david/llvm/build/lib/clang/10.0.0 -internal-isystem /usr/lib/gcc/x86_64-pc-linux-gnu/9.2.0/include/g++-v9 -internal-isystem /usr/lib/gcc/x86_64-pc-linux-gnu/9.2.0/include/g++-v9/x86_64-pc-linux-gnu -internal-isystem /usr/lib/gcc/x86_64-pc-linux-gnu/9.2.0/include/g++-v9/backward -internal-isystem /usr/local/include -internal-isystem /home/david/llvm/build/lib/clang/10.0.0/include -internal-externc-isystem /include -internal-externc-isystem /usr/include -Wfatal-errors -w -std=c++17 -fdeprecated-macro -fdebug-compilation-dir /home/david/tm5/reduce -ferror-limit 19 -fmessage-length 0 -fobjc-runtime=gcc -fcxx-exceptions -fexceptions -fdiagnostics-show-option -fcolor-diagnostics -o /dev/null -x c++ test.cpp

1. test.cpp:20:42: current parser token ';'
2. test.cpp:20:23: parsing function body 'operator=='
3. test.cpp:20:23: in compound statement ('{}')
4. test.cpp:8:16: instantiating variable definition 'is_valid<A>'
   #&#8203;0 0x000000000313ee4d PrintStackTraceSignalHandler(void*) (.llvm.14200593635904155002) (/home/david/llvm/build/bin/clang-10+0x313ee4d)
   #&#8203;1 0x000000000313c630 llvm::sys::RunSignalHandlers() (/home/david/llvm/build/bin/clang-10+0x313c630)
   #&#8203;2 0x000000000313f2e8 SignalHandler(int) (/home/david/llvm/build/bin/clang-10+0x313f2e8)
   #&#8203;3 0x00007f8f7f671660 __restore_rt (/lib64/libpthread.so.0+0x14660)
   #&#8203;4 0x00007f8f7f082d21 raise (/lib64/libc.so.6+0x38d21)
   #&#8203;5 0x00007f8f7f06c535 abort (/lib64/libc.so.6+0x22535)
   #&#8203;6 0x00007f8f7f06c40f _nl_load_domain.cold (/lib64/libc.so.6+0x2240f)
   #&#8203;7 0x00007f8f7f07a712 (/lib64/libc.so.6+0x30712)
   #&#8203;8 0x0000000004ccbf4f (/home/david/llvm/build/bin/clang-10+0x4ccbf4f)
   #&#8203;9 0x0000000004f15fc2 void llvm::function_ref<void ()>::callback_fn<clang::Sema::LookupConstructors(clang::CXXRecordDecl*)::$_13>(long) (/home/david/llvm/build/bin/clang-10+0x4f15fc2)
   #&#8203;10 0x0000000004efbf95 clang::Sema::LookupConstructors(clang::CXXRecordDecl*) (/home/david/llvm/build/bin/clang-10+0x4efbf95)
   #&#8203;11 0x0000000004fcd257 IsUserDefinedConversion(clang::Sema&, clang::Expr*, clang::QualType, clang::UserDefinedConversionSequence&, clang::OverloadCandidateSet&, bool, bool) (/home/david/llvm/build/bin/clang-10+0x4fcd257)
   #&#8203;12 0x0000000004ffffc0 TryUserDefinedConversion(clang::Sema&, clang::Expr*, clang::QualType, bool, bool, bool, bool, bool, bool) (/home/david/llvm/build/bin/clang-10+0x4ffffc0)
   #&#8203;13 0x0000000004fc6aff TryImplicitConversion(clang::Sema&, clang::Expr*, clang::QualType, bool, bool, bool, bool, bool, bool) (.llvm.5478737526472470733) (/home/david/llvm/build/bin/clang-10+0x4fc6aff)
   #&#8203;14 0x0000000004fd794d TryCopyInitialization(clang::Sema&, clang::Expr*, clang::QualType, bool, bool, bool, bool) (/home/david/llvm/build/bin/clang-10+0x4fd794d)
   #&#8203;15 0x0000000004fd6572 clang::Sema::AddOverloadCandidate(clang::FunctionDecl*, clang::DeclAccessPair, llvm::ArrayRef<clang::Expr*>, clang::OverloadCandidateSet&, bool, bool, bool, bool, clang::CallExpr::ADLCallKind, llvm::MutableArrayRef<clang::ImplicitConversionSequence>) (/home/david/llvm/build/bin/clang-10+0x4fd6572)
   #&#8203;16 0x0000000004fe3723 clang::Sema::AddArgumentDependentLookupCandidates(clang::DeclarationName, clang::SourceLocation, llvm::ArrayRef<clang::Expr*>, clang::TemplateArgumentListInfo*, clang::OverloadCandidateSet&, bool) (/home/david/llvm/build/bin/clang-10+0x4fe3723)
   #&#8203;17 0x0000000004ff343f clang::Sema::CreateOverloadedBinOp(clang::SourceLocation, clang::BinaryOperatorKind, clang::UnresolvedSetImpl const&, clang::Expr*, clang::Expr*, bool) (/home/david/llvm/build/bin/clang-10+0x4ff343f)
   #&#8203;18 0x000000000516e0c0 clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformCXXOperatorCallExpr(clang::CXXOperatorCallExpr*) (/home/david/llvm/build/bin/clang-10+0x516e0c0)
   #&#8203;19 0x00000000051ad93c clang::Sema::InstantiateVariableInitializer(clang::VarDecl*, clang::VarDecl*, clang::MultiLevelTemplateArgumentList const&) (/home/david/llvm/build/bin/clang-10+0x51ad93c)
   #&#8203;20 0x00000000051ad6ee clang::Sema::CompleteVarTemplateSpecializationDecl(clang::VarTemplateSpecializationDecl*, clang::VarDecl*, clang::MultiLevelTemplateArgumentList const&) (/home/david/llvm/build/bin/clang-10+0x51ad6ee)
   #&#8203;21 0x00000000051aee0d clang::Sema::InstantiateVariableDefinition(clang::SourceLocation, clang::VarDecl*, bool, bool, bool) (/home/david/llvm/build/bin/clang-10+0x51aee0d)
   #&#8203;22 0x0000000004dc0f3c DoMarkVarDeclReferenced(clang::Sema&, clang::SourceLocation, clang::VarDecl*, clang::Expr*) (.llvm.6274768002712316616) (/home/david/llvm/build/bin/clang-10+0x4dc0f3c)
   #&#8203;23 0x0000000004d6cb3d clang::Sema::BuildDeclRefExpr(clang::ValueDecl*, clang::QualType, clang::ExprValueKind, clang::DeclarationNameInfo const&, clang::NestedNameSpecifierLoc, clang::NamedDecl*, clang::SourceLocation, clang::TemplateArgumentListInfo const*) (/home/david/llvm/build/bin/clang-10+0x4d6cb3d)
   #&#8203;24 0x0000000004d72761 clang::Sema::BuildDeclarationNameExpr(clang::CXXScopeSpec const&, clang::DeclarationNameInfo const&, clang::NamedDecl*, clang::NamedDecl*, clang::TemplateArgumentListInfo const*, bool) (/home/david/llvm/build/bin/clang-10+0x4d72761)
   #&#8203;25 0x000000000507ab55 clang::Sema::CheckVarTemplateId(clang::CXXScopeSpec const&, clang::DeclarationNameInfo const&, clang::VarTemplateDecl*, clang::SourceLocation, clang::TemplateArgumentListInfo const*) (/home/david/llvm/build/bin/clang-10+0x507ab55)
   #&#8203;26 0x000000000517324c clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformUnresolvedLookupExpr(clang::UnresolvedLookupExpr*) (/home/david/llvm/build/bin/clang-10+0x517324c)
   #&#8203;27 0x00000000051786ec clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformTemplateArgument(clang::TemplateArgumentLoc const&, clang::TemplateArgumentLoc&, bool) (/home/david/llvm/build/bin/clang-10+0x51786ec)
   #&#8203;28 0x0000000005176e14 clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformTemplateSpecializationType(clang::TypeLocBuilder&, clang::TemplateSpecializationTypeLoc, clang::TemplateName) (/home/david/llvm/build/bin/clang-10+0x5176e14)
   #&#8203;29 0x000000000517656c clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformTSIInObjectScope(clang::TypeLoc, clang::QualType, clang::NamedDecl*, clang::CXXScopeSpec&) (/home/david/llvm/build/bin/clang-10+0x517656c)
   #&#8203;30 0x0000000005165278 clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformNestedNameSpecifierLoc(clang::NestedNameSpecifierLoc, clang::QualType, clang::NamedDecl*) (.llvm.209458239465659423) (/home/david/llvm/build/bin/clang-10+0x5165278)
   #&#8203;31 0x000000000517d8af clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformDependentNameType(clang::TypeLocBuilder&, clang::DependentNameTypeLoc, bool) (/home/david/llvm/build/bin/clang-10+0x517d8af)
   #&#8203;32 0x000000000514ff48 clang::TreeTransform<(anonymous namespace)::TemplateInstantiator>::TransformType(clang::TypeSourceInfo*) (.llvm.209458239465659423) (/home/david/llvm/build/bin/clang-10+0x514ff48)
   #&#8203;33 0x000000000507d989 SubstDefaultTemplateArgument(clang::Sema&, clang::TemplateDecl*, clang::SourceLocation, clang::SourceLocation, clang::TemplateTypeParmDecl*, llvm::SmallVectorImpl<clang::TemplateArgument>&) (/home/david/llvm/build/bin/clang-10+0x507d989)
   #&#8203;34 0x000000000507d446 clang::Sema::SubstDefaultTemplateArgumentIfAvailable(clang::TemplateDecl*, clang::SourceLocation, clang::SourceLocation, clang::Decl*, llvm::SmallVectorImpl<clang::TemplateArgument>&, bool&) (/home/david/llvm/build/bin/clang-10+0x507d446)
   #&#8203;35 0x000000000510b957 clang::Sema::FinishTemplateArgumentDeduction(clang::FunctionTemplateDecl*, llvm::SmallVectorImpl<clang::DeducedTemplateArgument>&, unsigned int, clang::FunctionDecl*&, clang::sema::TemplateDeductionInfo&, llvm::SmallVectorImpl<clang::Sema::OriginalCallArg> const*, bool, llvm::function_ref<bool ()>) (/home/david/llvm/build/bin/clang-10+0x510b957)
   #&#8203;36 0x000000000510dcc1 clang::Sema::DeduceTemplateArguments(clang::FunctionTemplateDecl*, clang::TemplateArgumentListInfo*, llvm::ArrayRef<clang::Expr*>, clang::FunctionDecl*&, clang::sema::TemplateDeductionInfo&, bool, llvm::function_ref<bool (llvm::ArrayRef<clang::QualType>)>) (/home/david/llvm/build/bin/clang-10+0x510dcc1)
   #&#8203;37 0x0000000004fdaff7 clang::Sema::AddTemplateOverloadCandidate(clang::FunctionTemplateDecl*, clang::DeclAccessPair, clang::TemplateArgumentListInfo*, llvm::ArrayRef<clang::Expr*>, clang::OverloadCandidateSet&, bool, bool, bool, clang::CallExpr::ADLCallKind) (/home/david/llvm/build/bin/clang-10+0x4fdaff7)
   #&#8203;38 0x0000000004efb845 clang::Sema::LookupSpecialMember(clang::CXXRecordDecl*, clang::Sema::CXXSpecialMember, bool, bool, bool, bool, bool) (/home/david/llvm/build/bin/clang-10+0x4efb845)
   #&#8203;39 0x0000000004cc5944 defaultedSpecialMemberIsConstexpr(clang::Sema&, clang::CXXRecordDecl*, clang::Sema::CXXSpecialMember, bool, clang::CXXConstructorDecl*, clang::Sema::InheritedConstructorInfo*) (/home/david/llvm/build/bin/clang-10+0x4cc5944)
   #&#8203;40 0x0000000004ccb81b clang::Sema::DeclareImplicitCopyConstructor(clang::CXXRecordDecl*) (/home/david/llvm/build/bin/clang-10+0x4ccb81b)
   #&#8203;41 0x0000000004f15fc2 void llvm::function_ref<void ()>::callback_fn<clang::Sema::LookupConstructors(clang::CXXRecordDecl*)::$_13>(long) (/home/david/llvm/build/bin/clang-10+0x4f15fc2)
   #&#8203;42 0x0000000004efbf95 clang::Sema::LookupConstructors(clang::CXXRecordDecl*) (/home/david/llvm/build/bin/clang-10+0x4efbf95)
   #&#8203;43 0x0000000004eb4656 TryConstructorInitialization(clang::Sema&, clang::InitializedEntity const&, clang::InitializationKind const&, llvm::MutableArrayRef<clang::Expr*>, clang::QualType, clang::QualType, clang::InitializationSequence&, bool, bool) (/home/david/llvm/build/bin/clang-10+0x4eb4656)
   #&#8203;44 0x0000000004eb0c3c clang::InitializationSequence::InitializeFrom(clang::Sema&, clang::InitializedEntity const&, clang::InitializationKind const&, llvm::MutableArrayRef<clang::Expr*>, bool, bool) (/home/david/llvm/build/bin/clang-10+0x4eb0c3c)
   #&#8203;45 0x0000000004bd3924 clang::Sema::AddInitializerToDecl(clang::Decl*, clang::Expr*, bool) (/home/david/llvm/build/bin/clang-10+0x4bd3924)
   #&#8203;46 0x00000000049b5d75 clang::Parser::ParseDeclarationAfterDeclaratorAndAttributes(clang::Declarator&, clang::Parser::ParsedTemplateInfo const&, clang::Parser::ForRangeInit*) (/home/david/llvm/build/bin/clang-10+0x49b5d75)
   #&#8203;47 0x00000000049b3b93 clang::Parser::ParseDeclGroup(clang::ParsingDeclSpec&, clang::DeclaratorContext, clang::SourceLocation*, clang::Parser::ForRangeInit*) (/home/david/llvm/build/bin/clang-10+0x49b3b93)
   #&#8203;48 0x00000000049add95 clang::Parser::ParseSimpleDeclaration(clang::DeclaratorContext, clang::SourceLocation&, clang::Parser::ParsedAttributesWithRange&, bool, clang::Parser::ForRangeInit*, clang::SourceLocation*) (/home/david/llvm/build/bin/clang-10+0x49add95)
   #&#8203;49 0x00000000049ad414 clang::Parser::ParseDeclaration(clang::DeclaratorContext, clang::SourceLocation&, clang::Parser::ParsedAttributesWithRange&, clang::SourceLocation*) (/home/david/llvm/build/bin/clang-10+0x49ad414)
   #&#8203;50 0x00000000049831d1 clang::Parser::ParseStatementOrDeclarationAfterAttributes(llvm::SmallVector<clang::Stmt*, 32u>&, clang::Parser::ParsedStmtContext, clang::SourceLocation*, clang::Parser::ParsedAttributesWithRange&) (/home/david/llvm/build/bin/clang-10+0x49831d1)
   #&#8203;51 0x0000000004982abb clang::Parser::ParseStatementOrDeclaration(llvm::SmallVector<clang::Stmt*, 32u>&, clang::Parser::ParsedStmtContext, clang::SourceLocation*) (/home/david/llvm/build/bin/clang-10+0x4982abb)
   #&#8203;52 0x000000000498c84e clang::Parser::ParseCompoundStatementBody(bool) (/home/david/llvm/build/bin/clang-10+0x498c84e)
   #&#8203;53 0x000000000498d8a2 clang::Parser::ParseFunctionStatementBody(clang::Decl*, clang::Parser::ParseScope&) (/home/david/llvm/build/bin/clang-10+0x498d8a2)
   #&#8203;54 0x000000000496a8cb clang::Parser::ParseFunctionDefinition(clang::ParsingDeclarator&, clang::Parser::ParsedTemplateInfo const&, clang::Parser::LateParsedAttrList*) (/home/david/llvm/build/bin/clang-10+0x496a8cb)
   #&#8203;55 0x00000000049b3a06 clang::Parser::ParseDeclGroup(clang::ParsingDeclSpec&, clang::DeclaratorContext, clang::SourceLocation*, clang::Parser::ForRangeInit*) (/home/david/llvm/build/bin/clang-10+0x49b3a06)
   #&#8203;56 0x000000000496965c clang::Parser::ParseDeclOrFunctionDefInternal(clang::Parser::ParsedAttributesWithRange&, clang::ParsingDeclSpec&, clang::AccessSpecifier) (/home/david/llvm/build/bin/clang-10+0x496965c)
   #&#8203;57 0x0000000004968f4f clang::Parser::ParseDeclarationOrFunctionDefinition(clang::Parser::ParsedAttributesWithRange&, clang::ParsingDeclSpec*, clang::AccessSpecifier) (/home/david/llvm/build/bin/clang-10+0x4968f4f)
   #&#8203;58 0x0000000004967d79 clang::Parser::ParseExternalDeclaration(clang::Parser::ParsedAttributesWithRange&, clang::ParsingDeclSpec*) (/home/david/llvm/build/bin/clang-10+0x4967d79)
   #&#8203;59 0x0000000004965a7d clang::Parser::ParseTopLevelDecl(clang::OpaquePtr<clang::DeclGroupRef>&, bool) (/home/david/llvm/build/bin/clang-10+0x4965a7d)
   #&#8203;60 0x0000000004960fb4 clang::ParseAST(clang::Sema&, bool, bool) (/home/david/llvm/build/bin/clang-10+0x4960fb4)
   #&#8203;61 0x0000000003ab7c1f clang::FrontendAction::Execute() (/home/david/llvm/build/bin/clang-10+0x3ab7c1f)
   #&#8203;62 0x0000000003a154d8 clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/home/david/llvm/build/bin/clang-10+0x3a154d8)
   #&#8203;63 0x0000000003b64067 clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/home/david/llvm/build/bin/clang-10+0x3b64067)
   #&#8203;64 0x000000000201134f cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (/home/david/llvm/build/bin/clang-10+0x201134f)
   #&#8203;65 0x000000000200f048 main (/home/david/llvm/build/bin/clang-10+0x200f048)
   #&#8203;66 0x00007f8f7f06df1b __libc_start_main (/lib64/libc.so.6+0x23f1b)
   #&#8203;67 0x000000000200c02a _start (/home/david/llvm/build/bin/clang-10+0x200c02a)
   clang-10: fatal error: unable to execute command: Aborted (core dumped)
   clang version 10.0.0 (https://github.com/llvm-project/llvm-project-20170507/ ca24486)
   Target: x86_64-unknown-linux-gnu
   Thread model: posix
   InstalledDir: /home/david/llvm/build/bin

[usx95]

Slightly reduced and shows stack exhaustion during template substitution.

https://godbolt.org/z/EnqTPG55W

template <bool>
struct enable_if {};

template <typename>
struct X {};

struct A {
    template <typename T, typename = typename enable_if<X<T>{} == X<T>{}>::type>
    A(T);
};

A &make_a();

bool operator==(A, A) {
    auto a = make_a();
    return true;
}

another example

https://godbolt.org/z/8zWfT4vha

template <bool>
struct enable_if {};

template <typename>
struct X {};

struct A {
    template <typename T, typename = typename enable_if<X<T>{} == X<T>{}>::type>
    A(T);
};

struct B {
    A a;
};

B &make_b();

bool operator==(A, A) {
    auto b = make_b();
    return true;
}