clang++ segfaults on (incorrect) template code

[llvmbot]

Bugzilla Link	10146
Version	2.9
OS	Linux
Attachments	Template classes causing clang++ segfault
Reporter	LLVM Bugzilla Contributor
CC	@asl,@DougGregor

Extended Description

When compiling the attached code, by invoking:

clang++ test.cc

causes a segmentation fault in both version 2.8 as included with Ubuntu x86_64, as well as with the LLVM supplied 2.9 x86_64 and i686 versions.

Stack dump:
0.      Program arguments: /home/gertjan/tmp/clang/clang+llvm-2.9-x86_64-linux.tar/bin/clang -cc1 -triple x86_64-unknown-linux-gnu -emit-obj -mrelax-all -disable-free -disable-llvm-verifier -main-file-name test.cc -mrelocation-model static -mdisable-fp-elim -masm-verbose -mconstructor-aliases -munwind-tables -target-cpu x86-64 -target-linker-version 2.21.0.20110327 -momit-leaf-frame-pointer -resource-dir /home/gertjan/tmp/clang/clang+llvm-2.9-x86_64-linux.tar/bin/../lib/clang/2.9 -ferror-limit 19 -fmessage-length 80 -fcxx-exceptions -fexceptions -fgnu-runtime -fdiagnostics-show-option -fcolor-diagnostics -o /tmp/cc-hc4Fnt.o -x c++ test.cc 
1.      test.cc:11:10: current parser token '{'
2.      test.cc:10:1: parsing struct/union/class body 'B'
clang: error: unable to execute command: Segmentation fault
clang: error: clang frontend command failed due to signal 1 (use -v to see invocation)

[asl]

Funny enough, it's still fails on ToT:

$ ./clang++ test.cc 
`test.cc:10:7: error: partial specialization of 'B' does not use any of its template parameters
class B<int> : public A<T> {
      ^
Assertion failed: (Kind.getKind() == InitializationKind::IK_Copy || Kind.isExplicitCast() || Kind.getKind() == InitializationKind::IK_DirectList), function Perform, file /Users/asl/Projects/llvm/2commit/llvm/tools/clang/lib/Sema/SemaInit.cpp, line 5001.

[zygoloid]

mentioned in issue llvm/llvm-bugzilla-archive#24658

[shafik]

code:

template <class T>
class A : public T {
};

template <class T>
class B : public A<T> {
};

template <class T>
class B<int> : public A<T> {
	B(T *t) {}
};

Still crashes: https://godbolt.org/z/dPG747Pbc

Assertion:

clang++: /root/llvm-project/clang/lib/Sema/SemaInit.cpp:8492:
clang::ExprResult clang::InitializationSequence::Perform(clang::Sema&, const clang::InitializedEntity&, const clang::InitializationKind&, clang::MultiExprArg, clang::QualType*): 
Assertion `Kind.getKind() == InitializationKind::IK_Copy || Kind.isExplicitCast() || Kind.getKind() == InitializationKind::IK_DirectList' 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-trunk/bin/clang++ -gdwarf-4 -g -o /app/output.s -mllvm --x86-asm-syntax=intel -S --gcc-toolchain=/opt/compiler-explorer/gcc-snapshot -fcolor-diagnostics -fno-crash-diagnostics <source>
1.	<source>:11:10: current parser token '{'
2.	<source>:10:1: parsing struct/union/class body 'B<int>'
 #0 0x000055ba4b5f2dbf llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3c12dbf)
 #1 0x000055ba4b5f0b2c llvm::sys::CleanupOnSignal(unsigned long) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3c10b2c)
 #2 0x000055ba4b53a1a8 CrashRecoverySignalHandler(int) CrashRecoveryContext.cpp:0:0
 #3 0x00007f1fdb424420 __restore_rt (/lib/x86_64-linux-gnu/libpthread.so.0+0x14420)
 #4 0x00007f1fdaef100b raise (/lib/x86_64-linux-gnu/libc.so.6+0x4300b)
 #5 0x00007f1fdaed0859 abort (/lib/x86_64-linux-gnu/libc.so.6+0x22859)
 #6 0x00007f1fdaed0729 (/lib/x86_64-linux-gnu/libc.so.6+0x22729)
 #7 0x00007f1fdaee1fd6 (/lib/x86_64-linux-gnu/libc.so.6+0x33fd6)
 #8 0x000055ba4e490532 clang::InitializationSequence::Perform(clang::Sema&, clang::InitializedEntity const&, clang::InitializationKind const&, llvm::MutableArrayRef<clang::Expr*>, clang::QualType*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6ab0532)
 #9 0x000055ba4e134313 BuildImplicitBaseInitializer(clang::Sema&, clang::CXXConstructorDecl*, ImplicitInitializerKind, clang::CXXBaseSpecifier*, bool, clang::CXXCtorInitializer*&) SemaDeclCXX.cpp:0:0
#10 0x000055ba4e18078c clang::Sema::SetCtorInitializers(clang::CXXConstructorDecl*, bool, llvm::ArrayRef<clang::CXXCtorInitializer*>) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x67a078c)
#11 0x000055ba4e18123d clang::Sema::ActOnDefaultCtorInitializers(clang::Decl*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x67a123d)
#12 0x000055ba4dd4f052 clang::Parser::ParseLexedMethodDef(clang::Parser::LexedMethod&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x636f052)
#13 0x000055ba4dd4ed6d clang::Parser::ParseLexedMethodDefs(clang::Parser::ParsingClass&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x636ed6d)
#14 0x000055ba4dd9addc clang::Parser::ParseCXXMemberSpecification(clang::SourceLocation, clang::SourceLocation, clang::ParsedAttributes&, unsigned int, clang::Decl*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x63baddc)
#15 0x000055ba4dd9ce48 clang::Parser::ParseClassSpecifier(clang::tok::TokenKind, clang::SourceLocation, clang::DeclSpec&, clang::Parser::ParsedTemplateInfo const&, clang::AccessSpecifier, bool, clang::Parser::DeclSpecContext, clang::ParsedAttributes&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x63bce48)
#16 0x000055ba4dd75b1d clang::Parser::ParseDeclarationSpecifiers(clang::DeclSpec&, clang::Parser::ParsedTemplateInfo const&, clang::AccessSpecifier, clang::Parser::DeclSpecContext, clang::Parser::LateParsedAttrList*, clang::ImplicitTypenameContext) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6395b1d)
#17 0x000055ba4de3b792 clang::Parser::ParseSingleDeclarationAfterTemplate(clang::DeclaratorContext, clang::Parser::ParsedTemplateInfo const&, clang::ParsingDeclRAIIObject&, clang::SourceLocation&, clang::ParsedAttributes&, clang::AccessSpecifier) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x645b792)
#18 0x000055ba4de41f66 clang::Parser::ParseTemplateDeclarationOrSpecialization(clang::DeclaratorContext, clang::SourceLocation&, clang::ParsedAttributes&, clang::AccessSpecifier) (.part.0) ParseTemplate.cpp:0:0
#19 0x000055ba4de421e3 clang::Parser::ParseDeclarationStartingWithTemplate(clang::DeclaratorContext, clang::SourceLocation&, clang::ParsedAttributes&, clang::AccessSpecifier) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x64621e3)
#20 0x000055ba4dd7c702 clang::Parser::ParseDeclaration(clang::DeclaratorContext, clang::SourceLocation&, clang::ParsedAttributes&, clang::ParsedAttributes&, clang::SourceLocation*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x639c702)
#21 0x000055ba4dd47954 clang::Parser::ParseExternalDeclaration(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6367954)
#22 0x000055ba4dd48896 clang::Parser::ParseTopLevelDecl(clang::OpaquePtr<clang::DeclGroupRef>&, clang::Sema::ModuleImportState&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6368896)
#23 0x000055ba4dd3c65a clang::ParseAST(clang::Sema&, bool, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x635c65a)
#24 0x000055ba4c8407c8 clang::CodeGenAction::ExecuteAction() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4e607c8)
#25 0x000055ba4c097f09 clang::FrontendAction::Execute() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x46b7f09)
#26 0x000055ba4c01c3d6 clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x463c3d6)
#27 0x000055ba4c17a9e6 clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x479a9e6)
#28 0x000055ba48aae46d cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x10ce46d)
#29 0x000055ba48aaa16a ExecuteCC1Tool(llvm::SmallVectorImpl<char const*>&, llvm::ToolContext const&) driver.cpp:0:0
#30 0x000055ba4be8439d 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
#31 0x000055ba4b53a6b0 llvm::CrashRecoveryContext::RunSafely(llvm::function_ref<void ()>) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3b5a6b0)
#32 0x000055ba4be849bf 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
#33 0x000055ba4be4c0ec clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&, clang::driver::Command const*&, bool) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x446c0ec)
#34 0x000055ba4be4cb7d 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+++0x446cb7d)
#35 0x000055ba4be54c5d clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4474c5d)
#36 0x000055ba48aac6ca clang_main(int, char**, llvm::ToolContext const&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x10cc6ca)
#37 0x000055ba489b3235 main (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xfd3235)
#38 0x00007f1fdaed2083 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x24083)
#39 0x000055ba48aa4f4e _start (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x10c4f4e)
clang++: error: clang frontend command failed with exit code 134 (use -v to see invocation)
Compiler returned: 134

[llvmbot]

@llvm/issue-subscribers-clang-frontend

[shafik]

This is the code block in that we are issuing the diagnostic before the crashes from Sema::ActOnClassTemplateSpecialization or Sema::ActOnVarTemplateSpecialization:

 // Find the class template (partial) specialization declaration that
  // corresponds to these arguments.
  if (isPartialSpecialization) {
    if (CheckTemplatePartialSpecializationArgs(TemplateNameLoc, ClassTemplate,
                                               TemplateArgs.size(),
                                               CanonicalConverted))
      return true;

    // FIXME: Move this to CheckTemplatePartialSpecializationArgs so we
    // also do it during instantiation.
    if (!Name.isDependent() &&
        !TemplateSpecializationType::anyDependentTemplateArguments(
            TemplateArgs, CanonicalConverted)) {
      Diag(TemplateNameLoc, diag::err_partial_spec_fully_specialized)
        << ClassTemplate->getDeclName();
      isPartialSpecialization = false;
    }
  }

The FIXME stands out here, it feels like we should return true; after the diagnostic but not sure.