| Issue |
61486
|
| Summary |
[c++20][concepts][clangd][AST] Crash in clangd due to assertion failure in ASTWriter.cpp:5814
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
yeswalrus
|
I am hitting a crash in clangd when indexing a large codebase's pch. After debugging, the code being parsed during the crash appears to be this:
```cpp
namespace fixed_containers
{
template <class StorageType>
concept IsFixedIndexBasedStorage = requires(const StorageType& a,
StorageType& b,
const std::size_t i)
{
...
};
```
The assertion at `ASTWriter.cpp:5814` is hit reliably. The cause appears to be `getTemplateArgsAsWritten()` returning null. Examining the definition, it appears that this can happen when the 2nd constructor overload for `ConceptSpecializationExpr` defined at `clang/lib/AST/ExprConcepts.cpp:73` is triggered, which always passes a nullptr for getTemplateArgsAsWritten(). Interestingly, Examining the _expression_ in GDB, getTemplateArguments() returns one value.
I'm unsure if this overload is incorrect and the expectation is that this argument is never not null or if the `VisitConceptSpecializationExpr` is simply missing a conditional.
Crash Backtrace:
```cpp
#29 0x0000557f32382b09 in clang::ASTRecordWriter::AddASTTemplateArgumentListInfo (this=0x7fb376018400, ASTTemplArgList=0x0) at /tools/build-llvmorg-16.0.0-rc4/source/clang/lib/Serialization/ASTWriter.cpp:5814
#30 0x0000557f323d4421 in clang::ASTStmtWriter::VisitConceptSpecializationExpr (this=0x7fb3760183f8, E=0x7fb33ae871a0) at /tools/build-llvmorg-16.0.0-rc4/source/clang/lib/Serialization/ASTWriterStmt.cpp:442
#31 0x0000557f323df69e in clang::StmtVisitorBase<std::add_pointer, clang::ASTStmtWriter, void>::Visit (this=0x7fb3760183f8, S=0x7fb33ae871a0) at tools/clang/include/clang/AST/StmtNodes.inc:1077
#32 0x0000557f323de51b in clang::ASTWriter::WriteSubStmt (this=0x7fb338095520, S=0x7fb33ae871a0) at /tools/build-llvmorg-16.0.0-rc4/source/clang/lib/Serialization/ASTWriterStmt.cpp:2756
#33 0x0000557f323dfd1b in clang::ASTRecordWriter::FlushStmts (this=0x7fb3760188b8) at /tools/build-llvmorg-16.0.0-rc4/source/clang/lib/Serialization/ASTWriterStmt.cpp:2771
#34 0x0000557f32368d43 in clang::ASTRecordWriter::Emit (this=0x7fb3760188b8, Code=112, Abbrev=0) at /tools/build-llvmorg-16.0.0-rc4/source/clang/include/clang/Serialization/ASTRecordWriter.h:96
#35 0x0000557f323ce966 in clang::ASTDeclWriter::Emit (this=0x7fb3760188a8, D=0x7fb33ae87090) at /tools/build-llvmorg-16.0.0-rc4/source/clang/lib/Serialization/ASTWriterDecl.cpp:53
#36 0x0000557f323ce6ac in clang::ASTWriter::WriteDecl (this=0x7fb338095520, Context=..., D=0x7fb33ae87090) at /tools/build-llvmorg-16.0.0-rc4/source/clang/lib/Serialization/ASTWriterDecl.cpp:2471
```
Creation Backtrace:
```cpp
#0 clang::ConceptSpecializationExpr::ConceptSpecializationExpr (this=0x7feea2e86920, C=..., NamedConcept=0x7fee31395a38, SpecDecl=0x7feea2e868e0, Satisfaction=0x0, Dependent=true, ContainsUnexpandedParameterPack=false)
at /tools/build-llvmorg-16.0.0-rc4/source/clang/lib/AST/ExprConcepts.cpp:88
#1 0x000055f2719ba0df in clang::ConceptSpecializationExpr::Create (C=..., NamedConcept=0x7fee31395a38, SpecDecl=0x7feea2e868e0, Satisfaction=0x0, Dependent=true, ContainsUnexpandedParameterPack=false)
at /tools/build-llvmorg-16.0.0-rc4/source/clang/lib/AST/ExprConcepts.cpp:103
#2 0x000055f2716ebc86 in canonicalizeImmediatelyDeclaredConstraint (C=..., IDC=0x7feea2e863f0, ConstrainedType=...) at /tools/build-llvmorg-16.0.0-rc4/source/clang/lib/AST/ASTContext.cpp:767
#3 0x000055f2716eb0e1 in clang::ASTContext::getCanonicalTemplateTemplateParmDecl (this=0x7feea007e200, TTP=0x7feea2e86530) at /tools/build-llvmorg-16.0.0-rc4/source/clang/lib/AST/ASTContext.cpp:808
#4 0x000055f27171561a in clang::ASTContext::getCanonicalTemplateName (this=0x7feea007e200, Name=...) at /tools/build-llvmorg-16.0.0-rc4/source/clang/lib/AST/ASTContext.cpp:6227
#5 0x000055f271714310 in clang::ASTContext::getCanonicalTemplateArgument (this=0x7feea007e200, Arg=...) at /tools/build-llvmorg-16.0.0-rc4/source/clang/lib/AST/ASTContext.cpp:6750
#6 0x000055f271715840 in getCanonicalTemplateArguments (C=..., Args=..., AnyNonCanonArgs=@0x7feed0a2a78f: true) at /tools/build-llvmorg-16.0.0-rc4/source/clang/lib/AST/ASTContext.cpp:3020
#7 0x000055f2717153f9 in clang::ASTContext::getCanonicalTemplateSpecializationType (this=0x7feea007e200, Template=..., Args=...) at /tools/build-llvmorg-16.0.0-rc4/source/clang/lib/AST/ASTContext.cpp:5001
#8 0x000055f2717150fb in clang::ASTContext::getTemplateSpecializationType (this=0x7feea007e200, Template=..., Args=..., Underlying=...) at /tools/build-llvmorg-16.0.0-rc4/source/clang/lib/AST/ASTContext.cpp:4970
#9 0x000055f27191cfb3 in clang::ClassTemplateDecl::getInjectedClassNameSpecialization (this=0x7feea2e86678) at /tools/build-llvmorg-16.0.0-rc4/source/clang/lib/AST/DeclTemplate.cpp:631
#10 0x000055f272c6ef71 in clang::Sema::CheckClassTemplate (this=0x7feea00f5a70, S=0x7feea027e1c0, TagSpec=26, TUK=clang::Sema::TUK_Definition, KWLoc=..., SS=..., Name=0x7fee313ec9c0, NameLoc=..., Attr=..., TemplateParams=0x7feea2e86588,
AS=clang::AS_none, ModulePrivateLoc=..., FriendLoc=..., NumOuterTemplateParamLists=0, OuterTemplateParamLists=0x7feed0a2fdd8, SkipBody=0x7feed0a2d2c8) at /tools/build-llvmorg-16.0.0-rc4/source/clang/lib/Sema/SemaTemplate.cpp:2106
#11 0x000055f2723c050a in clang::Sema::ActOnTag (this=0x7feea00f5a70, S=0x7feea027e1c0, TagSpec=26, TUK=clang::Sema::TUK_Definition, KWLoc=..., SS=..., Name=0x7fee313ec9c0, NameLoc=..., Attrs=..., AS=clang::AS_none, ModulePrivateLoc=...,
TemplateParameterLists=..., OwnedDecl=@0x7feed0a2d59b: false, IsDependent=@0x7feed0a2d59c: false, ScopedEnumKWLoc=..., ScopedEnumUsesClassTag=false, UnderlyingType=..., IsTypeSpecifier=false, IsTemplateParamOrArg=false,
OOK=clang::Sema::OOK_Outside, SkipBody=0x7feed0a2d2c8) at /tools/build-llvmorg-16.0.0-rc4/source/clang/lib/Sema/SemaDecl.cpp:16658
```
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