Hi,

I use LLVM (3.2) in my project (Qt 5.0.0) and it works as expected on Windows and OS X, but on Ubuntu it just crashes. If I start my application, don't use any of the LLVM-specific stuff in my application, and try to quit my application, then I get the following debug traces:

Qt Code: 
  1. 0	__memmove_ssse3	memcpy-ssse3.S	1682	0x1348f8c	
  2. 1	llvm::PassRegistry::removeRegistrationListener(llvm::PassRegistrationListener*)	/usr/lib/i386-linux-gnu/libLLVM-3.0.so.1		0xb0278ddb	
  3. 2	llvm::PassRegistrationListener::~PassRegistrationListener()	/usr/lib/i386-linux-gnu/libLLVM-3.0.so.1		0xb026aa06	
  4. 3	llvm::PassNameParser::~PassNameParser()	/usr/lib/i386-linux-gnu/libLLVM-3.0.so.1		0xb026aca2	
  5. 4	llvm::cl::list<llvm::PassInfo const*, bool, llvm::PassNameParser>::~list()	/home/me/myApp/build/plugins/myApp/libLLVM.so		0xb31eb8a4	
  6. 5	__run_exit_handlers	exit.c	78	0x1242f51	
  7. 6	__GI_exit	exit.c	100	0x1242fdd	
  8. 7	__libc_start_main	libc-start.c	258	0x12294db	
  9. 8	_start			0x8068ca1
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If you look at line 4, my application uses my version of LLVM (which I build as a Qt plugin), but then at lines 1, 2 and 3, we can see that my application somehow decided to use the system version of LLVM. Why is that? I have no idea!

All I know is that it used to work perfectly fine using Qt 4.8.x. I thought for a moment that it might be related to OpenGL/3D (Qt 5.0.0 uses OpenGL no matter what now, right?), especially since my Ubuntu box is in fact a virtual machine with no 3D acceleration (i.e. Mesa would take over and use llvmpipe?), but I then tried using the Ubuntu live CD (with 3D acceleration), and I got the same result, so I am puzzled...

Otherwise, if I manually rename the system version of LLVM (so that my application cannot 'see' it), then everything works as expected (i.e. no crash) but I obviously don't want and, in fact, can't really do that!

FWIW, here is another trace I get when starting my application and then trying to do some LLVM-specific stuff in my application:

Qt Code: 
  1. 0	llvm::FoldingSetNodeID::AddPointer(void const*)	/usr/lib/i386-linux-gnu/libLLVM-3.0.so.1		0xb074f37a	
  2. 1	clang::FunctionProtoType::Profile(llvm::FoldingSetNodeID&, clang::QualType, clang::QualType const*, unsigned int, clang::FunctionProtoType::ExtProtoInfo const&, clang::ASTContext const&)	/home/me/myApp/build/libLLVM.so		0x43a6b2e	
  3. 2	clang::FunctionProtoType::Profile(llvm::FoldingSetNodeID&, clang::ASTContext const&)	/home/me/myApp/build/libLLVM.so		0x43a6dd4	
  4. 3	llvm::ContextualFoldingSet<clang::FunctionProtoType, clang::ASTContext&>::NodeEquals(llvm::FoldingSetImpl::Node*, llvm::FoldingSetNodeID const&, unsigned int, llvm::FoldingSetNodeID&) const	/home/me/myApp/build/libLLVM.so		0x427d59f	
  5. 4	llvm::FoldingSetImpl::FindNodeOrInsertPos(llvm::FoldingSetNodeID const&, void*&)	/usr/lib/i386-linux-gnu/libLLVM-3.0.so.1		0xb074fb67	
  6. 5	clang::ASTContext::getFunctionType(clang::QualType, clang::QualType const*, unsigned int, clang::FunctionProtoType::ExtProtoInfo const&) const	/home/me/myApp/build/libLLVM.so		0x426ecbb	
  7. 6	clang::ASTContext::GetBuiltinType(unsigned int, clang::ASTContext::GetBuiltinTypeError&, unsigned int*) const	/home/me/myApp/build/libLLVM.so		0x4274243	
  8. 7	clang::Sema::LazilyCreateBuiltin(clang::IdentifierInfo*, unsigned int, clang::Scope*, bool, clang::SourceLocation)	/home/me/myApp/build/libLLVM.so		0x48baa24	
  9. 8	??	/home/me/myApp/build/libLLVM.so		0x49fde04	
  10. 9	clang::Sema::LookupName(clang::LookupResult&, clang::Scope*, bool)	/home/me/myApp/build/libLLVM.so		0x4a03d13	
  11. 10	clang::Sema::HandleDeclarator(clang::Scope*, clang::Declarator&, llvm::MutableArrayRef<clang::TemplateParameterList*>)	/home/me/myApp/build/libLLVM.so		0x48cb270	
  12. 11	clang::Sema::ActOnDeclarator(clang::Scope*, clang::Declarator&)	/home/me/myApp/build/libLLVM.so		0x48cb8f3	
  13. 12	clang::Parser::ParseDeclarationAfterDeclaratorAndAttributes(clang::Declarator&, clang::Parser::ParsedTemplateInfo const&)	/home/me/myApp/build/libLLVM.so		0x47196e1	
  14. 13	clang::Parser::ParseDeclGroup(clang::ParsingDeclSpec&, unsigned int, bool, clang::SourceLocation*, clang::Parser::ForRangeInit*)	/home/me/myApp/build/libLLVM.so		0x4725883	
  15. 14	clang::Parser::ParseDeclOrFunctionDefInternal(clang::Parser::ParsedAttributesWithRange&, clang::ParsingDeclSpec&, clang::AccessSpecifier)	/home/me/myApp/build/libLLVM.so		0x477563f	
  16. 15	clang::Parser::ParseDeclarationOrFunctionDefinition(clang::Parser::ParsedAttributesWithRange&, clang::ParsingDeclSpec*, clang::AccessSpecifier)	/home/me/myApp/build/libLLVM.so		0x4775d79	
  17. 16	clang::Parser::ParseExternalDeclaration(clang::Parser::ParsedAttributesWithRange&, clang::ParsingDeclSpec*)	/home/me/myApp/build/libLLVM.so		0x4779c77	
  18. 17	clang::Parser::ParseTopLevelDecl(clang::OpaquePtr<clang::DeclGroupRef>&)	/home/me/myApp/build/libLLVM.so		0x4779f48	
  19. 18	clang::ParseAST(clang::Sema&, bool, bool)	/home/me/myApp/build/libLLVM.so		0x470e49c	
  20. 19	clang::ASTFrontendAction::ExecuteAction()	/home/me/myApp/build/libLLVM.so		0x4671a57	
  21. 20	clang::CodeGenAction::ExecuteAction()	/home/me/myApp/build/libLLVM.so		0x456db42	
  22. ...	<More>
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Again, you can see that sometimes my application uses its version of LLVM while, at other times, it uses the system version of LLVM...!?

Now, I wouldn't expect many people to use LLVM in their project, but... how would you go about handling the case where your application uses its version of a library which is also used by your Linux system?...

Cheers, Alan.