<table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Issue</th>
<td>
<a href=https://github.com/llvm/llvm-project/issues/147186>147186</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>
[clang] ICE on invalid inheritance since version 6
</td>
</tr>
<tr>
<th>Labels</th>
<td>
clang
</td>
</tr>
<tr>
<th>Assignees</th>
<td>
</td>
</tr>
<tr>
<th>Reporter</th>
<td>
renehsz
</td>
</tr>
</table>
<pre>
The code below causes ICE on Clang since version 6. (Diagnostic compilation errors are expected, but not a compiler crash.)
```c++
class a : ;
class b : ;
struct c : virtual a;
template <typename d>
class e : c, d
using b::b;
```
Stack trace:
```
0. Program arguments: /usr/bin/clang++ -cc1 -triple x86_64-pc-linux-gnu -emit-obj -dumpdir code.o- -disable-free -clear-ast-before-backend -disable-llvm-verifier -discard-value-names -main-file-name code.cpp -mrelocation-model pic -pic-level 2 -pic-is-pie -mframe-pointer=all -fmath-errno -ffp-contract=on -fno-rounding-math -mconstructor-aliases -funwind-tables=2 -target-cpu x86-64 -tune-cpu generic -debugger-tuning=gdb -fdebug-compilation-dir=/home/r/projects/clang_bug -fcoverage-compilation-dir=/home/r/projects/clang_bug -resource-dir /usr/lib/clang/20 -internal-isystem /usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/15.1.1/../../../../include/c++/15.1.1 -internal-isystem /usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/15.1.1/../../../../include/c++/15.1.1/x86_64-pc-linux-gnu -internal-isystem /usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/15.1.1/../../../../include/c++/15.1.1/backward -internal-isystem /usr/lib/clang/20/include -internal-isystem /usr/local/include -internal-isystem /usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/15.1.1/../../../../x86_64-pc-linux-gnu/include -internal-externc-isystem /include -internal-externc-isystem /usr/include -fdeprecated-macro -ferror-limit 19 -stack-protector 2 -fgnuc-version=4.2.1 -fskip-odr-check-in-gmf -fcxx-exceptions -fexceptions -faddrsig -D__GCC_HAVE_DWARF2_CFI_ASM=1 -o /tmp/code-126fe3.o -x c++ code.cpp
1. code.cpp:6:11: current parser token ';'
2. code.cpp:5:1: parsing struct/union/class body 'e'
#0 0x00007fa71d2e09ce llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/usr/lib/libLLVM.so.20.1+0x8e09ce)
#1 0x00007fa71d2de047 (/usr/lib/libLLVM.so.20.1+0x8de047)
#2 0x00007fa71c44f600 (/usr/lib/libc.so.6+0x3d600)
#3 0x00007fa72764fbe5 clang::Sema::BuildUsingShadowDecl(clang::Scope*, clang::BaseUsingDecl*, clang::NamedDecl*, clang::UsingShadowDecl*) (/usr/lib/libclang-cpp.so.20.1+0x144fbe5)
#4 0x00007fa727654254 clang::Sema::BuildUsingDeclaration(clang::Scope*, clang::AccessSpecifier, clang::SourceLocation, bool, clang::SourceLocation, clang::CXXScopeSpec&, clang::DeclarationNameInfo, clang::SourceLocation, clang::ParsedAttributesView const&, bool, bool) (/usr/lib/libclang-cpp.so.20.1+0x1454254)
#5 0x00007fa727654a5c clang::Sema::ActOnUsingDeclaration(clang::Scope*, clang::AccessSpecifier, clang::SourceLocation, clang::SourceLocation, clang::CXXScopeSpec&, clang::UnqualifiedId&, clang::SourceLocation, clang::ParsedAttributesView const&) (/usr/lib/libclang-cpp.so.20.1+0x1454a5c)
#6 0x00007fa72695159e clang::Parser::ParseUsingDeclaration(clang::DeclaratorContext, clang::Parser::ParsedTemplateInfo const&, clang::SourceLocation, clang::SourceLocation&, clang::ParsedAttributes&, clang::AccessSpecifier) (/usr/lib/libclang-cpp.so.20.1+0x75159e)
#7 0x00007fa72692a9d1 clang::Parser::ParseCXXClassMemberDeclaration(clang::AccessSpecifier, clang::ParsedAttributes&, clang::Parser::ParsedTemplateInfo&, clang::ParsingDeclRAIIObject*) (/usr/lib/libclang-cpp.so.20.1+0x72a9d1)
#8 0x00007fa72692d920 clang::Parser::ParseCXXClassMemberDeclarationWithPragmas(clang::AccessSpecifier&, clang::ParsedAttributes&, clang::TypeSpecifierType, clang::Decl*) (/usr/lib/libclang-cpp.so.20.1+0x72d920)
#9 0x00007fa72692e081 clang::Parser::ParseCXXMemberSpecification(clang::SourceLocation, clang::SourceLocation, clang::ParsedAttributes&, unsigned int, clang::Decl*) (/usr/lib/libclang-cpp.so.20.1+0x72e081)
#10 0x00007fa7269305fd clang::Parser::ParseClassSpecifier(clang::tok::TokenKind, clang::SourceLocation, clang::DeclSpec&, clang::Parser::ParsedTemplateInfo&, clang::AccessSpecifier, bool, clang::Parser::DeclSpecContext, clang::ParsedAttributes&) (/usr/lib/libclang-cpp.so.20.1+0x7305fd)
#11 0x00007fa7269321c5 clang::Parser::ParseDeclarationSpecifiers(clang::DeclSpec&, clang::Parser::ParsedTemplateInfo&, clang::AccessSpecifier, clang::Parser::DeclSpecContext, clang::Parser::LateParsedAttrList*, clang::ImplicitTypenameContext) (/usr/lib/libclang-cpp.so.20.1+0x7321c5)
#12 0x00007fa7269de5a6 clang::Parser::ParseDeclarationAfterTemplate(clang::DeclaratorContext, clang::Parser::ParsedTemplateInfo&, clang::ParsingDeclRAIIObject&, clang::SourceLocation&, clang::ParsedAttributes&, clang::AccessSpecifier) (/usr/lib/libclang-cpp.so.20.1+0x7de5a6)
#13 0x00007fa7269ecf81 clang::Parser::ParseTemplateDeclarationOrSpecialization(clang::DeclaratorContext, clang::SourceLocation&, clang::ParsedAttributes&, clang::AccessSpecifier) (/usr/lib/libclang-cpp.so.20.1+0x7ecf81)
#14 0x00007fa7269ed23b clang::Parser::ParseDeclarationStartingWithTemplate(clang::DeclaratorContext, clang::SourceLocation&, clang::ParsedAttributes&) (/usr/lib/libclang-cpp.so.20.1+0x7ed23b)
#15 0x00007fa72695b207 clang::Parser::ParseDeclaration(clang::DeclaratorContext, clang::SourceLocation&, clang::ParsedAttributes&, clang::ParsedAttributes&, clang::SourceLocation*) (/usr/lib/libclang-cpp.so.20.1+0x75b207)
#16 0x00007fa7269f4ea2 clang::Parser::ParseExternalDeclaration(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec*) (/usr/lib/libclang-cpp.so.20.1+0x7f4ea2)
#17 0x00007fa7269f58eb clang::Parser::ParseTopLevelDecl(clang::OpaquePtr<clang::DeclGroupRef>&, clang::Sema::ModuleImportState&) (/usr/lib/libclang-cpp.so.20.1+0x7f58eb)
#18 0x00007fa7268fe36b clang::ParseAST(clang::Sema&, bool, bool) (/usr/lib/libclang-cpp.so.20.1+0x6fe36b)
#19 0x00007fa728a0f8b8 clang::FrontendAction::Execute() (/usr/lib/libclang-cpp.so.20.1+0x280f8b8)
#20 0x00007fa728998897 clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/usr/lib/libclang-cpp.so.20.1+0x2798897)
#21 0x00007fa728a760d0 clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/usr/lib/libclang-cpp.so.20.1+0x28760d0)
#22 0x0000561cb535d625 cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (/usr/bin/clang+++0x14625)
#23 0x0000561cb5361568 (/usr/bin/clang+++0x18568)
#24 0x0000561cb5362fa7 clang_main(int, char**, llvm::ToolContext const&) (/usr/bin/clang+++0x19fa7)
#25 0x0000561cb53541c6 main (/usr/bin/clang+++0xb1c6)
#26 0x00007fa71c43952e __libc_start_call_main /usr/src/debug/glibc/glibc/csu/../sysdeps/nptl/libc_start_call_main.h:74:3
#27 0x00007fa71c4395ea call_init /usr/src/debug/glibc/glibc/csu/../csu/libc-start.c:128:20
#28 0x00007fa71c4395ea __libc_start_main /usr/src/debug/glibc/glibc/csu/../csu/libc-start.c:347:5
#29 0x0000561cb5354225 _start (/usr/bin/clang+++0xb225)
clang++: error: unable to execute command: Segmentation fault
```
Run script: [code-22a624.sh](https://github.com/user-attachments/files/21088705/code-22a624.sh.txt)
</pre>
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