Compiler crash with old Clang

[sergemeynard-triton]

I am building the library using Clang 3.4.2 (I don't currently have access to a more recent version) and it is crashing the compiler. The crash goes away if I disable the specialization of std::swap at line 17194, and my app still seems to work properly, but I wanted to get a second opinion about how safe this patch actually is...

[nlohmann]

How does the exact error message look like?

[sergemeynard-triton]

[exec] 0 libLLVM-3.4.so 0x00007f42384485d2 llvm::sys::PrintStackTrace(_IO_FILE*) + 34
[exec] 1 libLLVM-3.4.so 0x00007f4238448dfa
[exec] 2 libpthread.so.0 0x00007f42372a77e0
[exec] 3 clang 0x0000000000bb3a76
[exec] 4 clang 0x0000000000bb441d
[exec] 5 clang 0x0000000000bb4833
[exec] 6 clang 0x0000000000bb4c8a
[exec] 7 clang 0x0000000000bb1f54 clang::Sema::AddOverloadCandidate(clang::FunctionDecl*, clang::DeclAccessPair, llvm::ArrayRefclang::Expr*, clang::OverloadCandidateSet&, bool, bool, bool) + 1188
[exec] 8 clang 0x0000000000bb245d clang::Sema::AddTemplateOverloadCandidate(clang::FunctionTemplateDecl*, clang::DeclAccessPair, clang::TemplateArgumentListInfo*, llvm::ArrayRefclang::Expr*, clang::OverloadCandidateSet&, bool) + 685
[exec] 9 clang 0x0000000000bbf2c6 clang::Sema::AddOverloadedCallCandidates(clang::UnresolvedLookupExpr*, llvm::ArrayRefclang::Expr*, clang::OverloadCandidateSet&, bool) + 262
[exec] 10 clang 0x0000000000bbf505 clang::Sema::buildOverloadedCallSet(clang::Scope*, clang::Expr*, clang::UnresolvedLookupExpr*, llvm::MutableArrayRefclang::Expr*, clang::SourceLocation, clang::OverloadCandidateSet*, clang::ActionResult<clang::Expr*, true>) + 325
[exec] 11 clang 0x0000000000bc648c clang::Sema::BuildOverloadedCallExpr(clang::Scope, clang::Expr*, clang::UnresolvedLookupExpr*, clang::SourceLocation, llvm::MutableArrayRefclang::Expr*, clang::SourceLocation, clang::Expr*, bool) + 332
[exec] 12 clang 0x0000000000afc7d3 clang::Sema::ActOnCallExpr(clang::Scope*, clang::Expr*, clang::SourceLocation, llvm::MutableArrayRefclang::Expr*, clang::SourceLocation, clang::Expr*, bool) + 1187
[exec] 13 clang 0x0000000000c8fe91
[exec] 14 clang 0x0000000000c73955
[exec] 15 clang 0x0000000000c7ce62
[exec] 16 clang 0x0000000000c7d95c
[exec] 17 clang 0x0000000000c7443d
[exec] 18 clang 0x0000000000c77e05
[exec] 19 clang 0x0000000000c7bc6b
[exec] 20 clang 0x0000000000c7bdff
[exec] 21 clang 0x0000000000c7cc3e
[exec] 22 clang 0x0000000000c7d95c
[exec] 23 clang 0x0000000000c7e33d clang::Sema::SubstType(clang::TypeSourceInfo*, clang::MultiLevelTemplateArgumentList const&, clang::SourceLocation, clang::DeclarationName) + 93
[exec] 24 clang 0x0000000000c7e7ce clang::Sema::SubstBaseSpecifiers(clang::CXXRecordDecl*, clang::CXXRecordDecl*, clang::MultiLevelTemplateArgumentList const&) + 1118
[exec] 25 clang 0x0000000000c871cc clang::Sema::InstantiateClass(clang::SourceLocation, clang::CXXRecordDecl*, clang::CXXRecordDecl*, clang::MultiLevelTemplateArgumentList const&, clang::TemplateSpecializationKind, bool) + 700
[exec] 26 clang 0x0000000000c890b8 clang::Sema::InstantiateClassTemplateSpecialization(clang::SourceLocation, clang::ClassTemplateSpecializationDecl*, clang::TemplateSpecializationKind, bool) + 3016
[exec] 27 clang 0x0000000000cc77ac clang::Sema::RequireCompleteTypeImpl(clang::SourceLocation, clang::QualType, clang::Sema::TypeDiagnoser&) + 1708
[exec] 28 clang 0x0000000000cc78ee clang::Sema::RequireCompleteType(clang::SourceLocation, clang::QualType, clang::Sema::TypeDiagnoser&) + 30
[exec] 29 clang 0x0000000000a732d4 clang::Sema::CheckBaseSpecifier(clang::CXXRecordDecl*, clang::SourceRange, bool, clang::AccessSpecifier, clang::TypeSourceInfo*, clang::SourceLocation) + 2116
[exec] 30 clang 0x0000000000c7e824 clang::Sema::SubstBaseSpecifiers(clang::CXXRecordDecl*, clang::CXXRecordDecl*, clang::MultiLevelTemplateArgumentList const&) + 1204
[exec] 31 clang 0x0000000000c871cc clang::Sema::InstantiateClass(clang::SourceLocation, clang::CXXRecordDecl*, clang::CXXRecordDecl*, clang::MultiLevelTemplateArgumentList const&, clang::TemplateSpecializationKind, bool) + 700
[exec] 32 clang 0x0000000000c890b8 clang::Sema::InstantiateClassTemplateSpecialization(clang::SourceLocation, clang::ClassTemplateSpecializationDecl*, clang::TemplateSpecializationKind, bool) + 3016
[exec] 33 clang 0x0000000000cc77ac clang::Sema::RequireCompleteTypeImpl(clang::SourceLocation, clang::QualType, clang::Sema::TypeDiagnoser&) + 1708
[exec] 34 clang 0x0000000000cc78ee clang::Sema::RequireCompleteType(clang::SourceLocation, clang::QualType, clang::Sema::TypeDiagnoser&) + 30
[exec] 35 clang 0x0000000000a732d4 clang::Sema::CheckBaseSpecifier(clang::CXXRecordDecl*, clang::SourceRange, bool, clang::AccessSpecifier, clang::TypeSourceInfo*, clang::SourceLocation) + 2116
[exec] 36 clang 0x0000000000c7e824 clang::Sema::SubstBaseSpecifiers(clang::CXXRecordDecl*, clang::CXXRecordDecl*, clang::MultiLevelTemplateArgumentList const&) + 1204
[exec] 37 clang 0x0000000000c871cc clang::Sema::InstantiateClass(clang::SourceLocation, clang::CXXRecordDecl*, clang::CXXRecordDecl*, clang::MultiLevelTemplateArgumentList const&, clang::TemplateSpecializationKind, bool) + 700
[exec] 38 clang 0x0000000000c890b8 clang::Sema::InstantiateClassTemplateSpecialization(clang::SourceLocation, clang::ClassTemplateSpecializationDecl*, clang::TemplateSpecializationKind, bool) + 3016
[exec] 39 clang 0x0000000000cc77ac clang::Sema::RequireCompleteTypeImpl(clang::SourceLocation, clang::QualType, clang::Sema::TypeDiagnoser&) + 1708
[exec] 40 clang 0x0000000000cc78ee clang::Sema::RequireCompleteType(clang::SourceLocation, clang::QualType, clang::Sema::TypeDiagnoser&) + 30
[exec] 41 clang 0x0000000000977f49 clang::Sema::RequireCompleteDeclContext(clang::CXXScopeSpec&, clang::DeclContext*) + 313
[exec] 42 clang 0x0000000000af1026 clang::Sema::BuildQualifiedDeclarationNameExpr(clang::CXXScopeSpec&, clang::DeclarationNameInfo const&, bool) + 102
[exec] 43 clang 0x0000000000c6b3a8
[exec] 44 clang 0x0000000000c84f33
[exec] 45 clang 0x0000000000c8501b
[exec] 46 clang 0x0000000000c73a97
[exec] 47 clang 0x0000000000c743a1
[exec] 48 clang 0x0000000000c77e05
[exec] 49 clang 0x0000000000c7c86f
[exec] 50 clang 0x0000000000c7d95c
[exec] 51 clang 0x0000000000c7e33d clang::Sema::SubstType(clang::TypeSourceInfo*, clang::MultiLevelTemplateArgumentList const&, clang::SourceLocation, clang::DeclarationName) + 93
[exec] 52 clang 0x0000000000c7e7ce clang::Sema::SubstBaseSpecifiers(clang::CXXRecordDecl*, clang::CXXRecordDecl*, clang::MultiLevelTemplateArgumentList const&) + 1118
[exec] 53 clang 0x0000000000c871cc clang::Sema::InstantiateClass(clang::SourceLocation, clang::CXXRecordDecl*, clang::CXXRecordDecl*, clang::MultiLevelTemplateArgumentList const&, clang::TemplateSpecializationKind, bool) + 700
[exec] 54 clang 0x0000000000c890b8 clang::Sema::InstantiateClassTemplateSpecialization(clang::SourceLocation, clang::ClassTemplateSpecializationDecl*, clang::TemplateSpecializationKind, bool) + 3016
[exec] 55 clang 0x0000000000cc77ac clang::Sema::RequireCompleteTypeImpl(clang::SourceLocation, clang::QualType, clang::Sema::TypeDiagnoser&) + 1708
[exec] 56 clang 0x0000000000cc78ee clang::Sema::RequireCompleteType(clang::SourceLocation, clang::QualType, clang::Sema::TypeDiagnoser&) + 30
[exec] 57 clang 0x0000000000a732d4 clang::Sema::CheckBaseSpecifier(clang::CXXRecordDecl*, clang::SourceRange, bool, clang::AccessSpecifier, clang::TypeSourceInfo*, clang::SourceLocation) + 2116
[exec] 58 clang 0x0000000000c7e824 clang::Sema::SubstBaseSpecifiers(clang::CXXRecordDecl*, clang::CXXRecordDecl*, clang::MultiLevelTemplateArgumentList const&) + 1204
[exec] 59 clang 0x0000000000c871cc clang::Sema::InstantiateClass(clang::SourceLocation, clang::CXXRecordDecl*, clang::CXXRecordDecl*, clang::MultiLevelTemplateArgumentList const&, clang::TemplateSpecializationKind, bool) + 700
[exec] 60 clang 0x0000000000c890b8 clang::Sema::InstantiateClassTemplateSpecialization(clang::SourceLocation, clang::ClassTemplateSpecializationDecl*, clang::TemplateSpecializationKind, bool) + 3016
[exec] 61 clang 0x0000000000cc77ac clang::Sema::RequireCompleteTypeImpl(clang::SourceLocation, clang::QualType, clang::Sema::TypeDiagnoser&) + 1708
[exec] 62 clang 0x0000000000cc78ee clang::Sema::RequireCompleteType(clang::SourceLocation, clang::QualType, clang::Sema::TypeDiagnoser&) + 30
[exec] 63 clang 0x0000000000977f49 clang::Sema::RequireCompleteDeclContext(clang::CXXScopeSpec&, clang::DeclContext*) + 313
[exec] 64 clang 0x00000000009f6f6d clang::Sema::getTypeName(clang::IdentifierInfo const&, clang::SourceLocation, clang::Scope*, clang::CXXScopeSpec*, bool, bool, clang::OpaquePtrclang::QualType, bool, bool, clang::IdentifierInfo**) + 2349
[exec] 65 clang 0x00000000008d387b clang::Parser::TryAnnotateTypeOrScopeTokenAfterScopeSpec(bool, bool, clang::CXXScopeSpec&, bool) + 331
[exec] 66 clang 0x00000000008d4099 clang::Parser::TryAnnotateTypeOrScopeToken(bool, bool) + 169
[exec] 67 clang 0x0000000000906a3c clang::Parser::ParseCastExpression(bool, bool, bool&, clang::Parser::TypeCastState) + 5964
[exec] 68 clang 0x0000000000906c0d clang::Parser::ParseCastExpression(bool, bool, clang::Parser::TypeCastState) + 29
[exec] 69 clang 0x000000000090c68d clang::Parser::ParseConstantExpression(clang::Parser::TypeCastState) + 61
[exec] 70 clang 0x00000000008f583b clang::Parser::tryParseExceptionSpecification(clang::SourceRange&, llvm::SmallVectorImpl<clang::OpaquePtrclang::QualType >&, llvm::SmallVectorImplclang::SourceRange&, clang::ActionResult<clang::Expr*, true>&) + 555
[exec] 71 clang 0x00000000008ed815 clang::Parser::ParseFunctionDeclarator(clang::Declarator&, clang::ParsedAttributes&, clang::BalancedDelimiterTracker&, bool, bool) + 3013
[exec] 72 clang 0x00000000008ee5e5 clang::Parser::ParseDirectDeclarator(clang::Declarator&) + 1221
[exec] 73 clang 0x00000000008e4c17 clang::Parser::ParseDeclaratorInternal(clang::Declarator&, void (clang::Parser::)(clang::Declarator&)) + 535
[exec] 74 clang 0x00000000009434fa clang::Parser::ParseSingleDeclarationAfterTemplate(unsigned int, clang::Parser::ParsedTemplateInfo const&, clang::ParsingDeclRAIIObject&, clang::SourceLocation&, clang::AccessSpecifier, clang::AttributeList) + 1514
[exec] 75 clang 0x0000000000944c05 clang::Parser::ParseTemplateDeclarationOrSpecialization(unsigned int, clang::SourceLocation&, clang::AccessSpecifier, clang::AttributeList*) + 741
[exec] 76 clang 0x0000000000944f9f clang::Parser::ParseDeclarationStartingWithTemplate(unsigned int, clang::SourceLocation&, clang::AccessSpecifier, clang::AttributeList*) + 143
[exec] 77 clang 0x00000000008eba3e clang::Parser::ParseDeclaration(llvm::SmallVector<clang::Stmt*, 32u>&, unsigned int, clang::SourceLocation&, clang::Parser::ParsedAttributesWithRange&) + 766
[exec] 78 clang 0x00000000008d2e5e clang::Parser::ParseExternalDeclaration(clang::Parser::ParsedAttributesWithRange&, clang::ParsingDeclSpec*) + 1374
[exec] 79 clang 0x00000000008f48d3 clang::Parser::ParseInnerNamespace(std::vector<clang::SourceLocation, std::allocatorclang::SourceLocation >&, std::vector<clang::IdentifierInfo*, std::allocatorclang::IdentifierInfo* >&, std::vector<clang::SourceLocation, std::allocatorclang::SourceLocation >&, unsigned int, clang::SourceLocation&, clang::ParsedAttributes&, clang::BalancedDelimiterTracker&) + 387
[exec] 80 clang 0x00000000008f7509 clang::Parser::ParseNamespace(unsigned int, clang::SourceLocation&, clang::SourceLocation) + 3785
[exec] 81 clang 0x00000000008eba94 clang::Parser::ParseDeclaration(llvm::SmallVector<clang::Stmt*, 32u>&, unsigned int, clang::SourceLocation&, clang::Parser::ParsedAttributesWithRange&) + 852
[exec] 82 clang 0x00000000008d2e5e clang::Parser::ParseExternalDeclaration(clang::Parser::ParsedAttributesWithRange&, clang::ParsingDeclSpec*) + 1374
[exec] 83 clang 0x00000000008d3565 clang::Parser::ParseTopLevelDecl(clang::OpaquePtrclang::DeclGroupRef&) + 181
[exec] 84 clang 0x00000000008c9e4b clang::ParseAST(clang::Sema&, bool, bool) + 459
[exec] 85 clang 0x000000000073ab46 clang::CodeGenAction::ExecuteAction() + 70
[exec] 86 clang 0x00000000005bccf2 clang::FrontendAction::Execute() + 210
[exec] 87 clang 0x00000000005982cd clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) + 285
[exec] 88 clang 0x000000000057dc5a clang::ExecuteCompilerInvocation(clang::CompilerInstance*) + 1642
[exec] 89 clang 0x0000000000573bc0 cc1_main(char const**, char const**, char const*, void*) + 1184
[exec] 90 clang 0x000000000057c264 main + 7636
[exec] 91 libc.so.6 0x00007f4235f4dd1d __libc_start_main + 253
[exec] 92 clang 0x0000000000573529

clang: error: unable to execute command: Segmentation fault (core dumped)

[nlohmann]

Do you mean this?

https://github.com/nlohmann/json/blob/develop/single_include/nlohmann/json.hpp#L18492

[sergemeynard-triton]

Yes, I believe that's the one. I wrapped the whole thing inside a #ifndef JSON_DISABLE_SWAP_SPECIALIZATION so I could turn it on or off easily from the including file.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[LEgregius]

I was having the same problem, and I found that if I simply move the swap down under the less specialization, the crash goes away. ¯_(ツ)_/¯

[nlohmann]

@LEgregius Could you provide more details on the fix?

@evilsquirrel Could you try the idea from #1179 (comment)?

[sergemeynard-triton]

It seems to fix the crash, yes. The last time I fixed a compiler crash by swapping lines of code was over 20 years ago, so good catch :)

[LEgregius]

I forked it and made modified version. I'll make a pull request a bit later.