Problem using LLVM with Qt 5.0.0 within on Ubuntu

[agarny]

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:

0	__memmove_ssse3	memcpy-ssse3.S	1682	0x1348f8c	
1	llvm::PassRegistry::removeRegistrationListener(llvm::PassRegistrationListener*)	/usr/lib/i386-linux-gnu/libLLVM-3.0.so.1		0xb0278ddb	
2	llvm::PassRegistrationListener::~PassRegistrationListener()	/usr/lib/i386-linux-gnu/libLLVM-3.0.so.1		0xb026aa06	
3	llvm::PassNameParser::~PassNameParser()	/usr/lib/i386-linux-gnu/libLLVM-3.0.so.1		0xb026aca2	
4	llvm::cl::list<llvm::PassInfo const*, bool, llvm::PassNameParser>::~list()	/home/me/myApp/build/plugins/myApp/libLLVM.so		0xb31eb8a4	
5	__run_exit_handlers	exit.c	78	0x1242f51	
6	__GI_exit	exit.c	100	0x1242fdd	
7	__libc_start_main	libc-start.c	258	0x12294db	
8	_start			0x8068ca1

0	__memmove_ssse3	memcpy-ssse3.S	1682	0x1348f8c	
1	llvm::PassRegistry::removeRegistrationListener(llvm::PassRegistrationListener*)	/usr/lib/i386-linux-gnu/libLLVM-3.0.so.1		0xb0278ddb	
2	llvm::PassRegistrationListener::~PassRegistrationListener()	/usr/lib/i386-linux-gnu/libLLVM-3.0.so.1		0xb026aa06	
3	llvm::PassNameParser::~PassNameParser()	/usr/lib/i386-linux-gnu/libLLVM-3.0.so.1		0xb026aca2	
4	llvm::cl::list<llvm::PassInfo const*, bool, llvm::PassNameParser>::~list()	/home/me/myApp/build/plugins/myApp/libLLVM.so		0xb31eb8a4	
5	__run_exit_handlers	exit.c	78	0x1242f51	
6	__GI_exit	exit.c	100	0x1242fdd	
7	__libc_start_main	libc-start.c	258	0x12294db	
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:

0	llvm::FoldingSetNodeID::AddPointer(void const*)	/usr/lib/i386-linux-gnu/libLLVM-3.0.so.1		0xb074f37a	
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	
2	clang::FunctionProtoType::Profile(llvm::FoldingSetNodeID&, clang::ASTContext const&)	/home/me/myApp/build/libLLVM.so		0x43a6dd4	
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	
4	llvm::FoldingSetImpl::FindNodeOrInsertPos(llvm::FoldingSetNodeID const&, void*&)	/usr/lib/i386-linux-gnu/libLLVM-3.0.so.1		0xb074fb67	
5	clang::ASTContext::getFunctionType(clang::QualType, clang::QualType const*, unsigned int, clang::FunctionProtoType::ExtProtoInfo const&) const	/home/me/myApp/build/libLLVM.so		0x426ecbb	
6	clang::ASTContext::GetBuiltinType(unsigned int, clang::ASTContext::GetBuiltinTypeError&, unsigned int*) const	/home/me/myApp/build/libLLVM.so		0x4274243	
7	clang::Sema::LazilyCreateBuiltin(clang::IdentifierInfo*, unsigned int, clang::Scope*, bool, clang::SourceLocation)	/home/me/myApp/build/libLLVM.so		0x48baa24	
8	??	/home/me/myApp/build/libLLVM.so		0x49fde04	
9	clang::Sema::LookupName(clang::LookupResult&, clang::Scope*, bool)	/home/me/myApp/build/libLLVM.so		0x4a03d13	
10	clang::Sema::HandleDeclarator(clang::Scope*, clang::Declarator&, llvm::MutableArrayRef<clang::TemplateParameterList*>)	/home/me/myApp/build/libLLVM.so		0x48cb270	
11	clang::Sema::ActOnDeclarator(clang::Scope*, clang::Declarator&)	/home/me/myApp/build/libLLVM.so		0x48cb8f3	
12	clang::Parser::ParseDeclarationAfterDeclaratorAndAttributes(clang::Declarator&, clang::Parser::ParsedTemplateInfo const&)	/home/me/myApp/build/libLLVM.so		0x47196e1	
13	clang::Parser::ParseDeclGroup(clang::ParsingDeclSpec&, unsigned int, bool, clang::SourceLocation*, clang::Parser::ForRangeInit*)	/home/me/myApp/build/libLLVM.so		0x4725883	
14	clang::Parser::ParseDeclOrFunctionDefInternal(clang::Parser::ParsedAttributesWithRange&, clang::ParsingDeclSpec&, clang::AccessSpecifier)	/home/me/myApp/build/libLLVM.so		0x477563f	
15	clang::Parser::ParseDeclarationOrFunctionDefinition(clang::Parser::ParsedAttributesWithRange&, clang::ParsingDeclSpec*, clang::AccessSpecifier)	/home/me/myApp/build/libLLVM.so		0x4775d79	
16	clang::Parser::ParseExternalDeclaration(clang::Parser::ParsedAttributesWithRange&, clang::ParsingDeclSpec*)	/home/me/myApp/build/libLLVM.so		0x4779c77	
17	clang::Parser::ParseTopLevelDecl(clang::OpaquePtr<clang::DeclGroupRef>&)	/home/me/myApp/build/libLLVM.so		0x4779f48	
18	clang::ParseAST(clang::Sema&, bool, bool)	/home/me/myApp/build/libLLVM.so		0x470e49c	
19	clang::ASTFrontendAction::ExecuteAction()	/home/me/myApp/build/libLLVM.so		0x4671a57	
20	clang::CodeGenAction::ExecuteAction()	/home/me/myApp/build/libLLVM.so		0x456db42	
...	<More>

0	llvm::FoldingSetNodeID::AddPointer(void const*)	/usr/lib/i386-linux-gnu/libLLVM-3.0.so.1		0xb074f37a	
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	
2	clang::FunctionProtoType::Profile(llvm::FoldingSetNodeID&, clang::ASTContext const&)	/home/me/myApp/build/libLLVM.so		0x43a6dd4	
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	
4	llvm::FoldingSetImpl::FindNodeOrInsertPos(llvm::FoldingSetNodeID const&, void*&)	/usr/lib/i386-linux-gnu/libLLVM-3.0.so.1		0xb074fb67	
5	clang::ASTContext::getFunctionType(clang::QualType, clang::QualType const*, unsigned int, clang::FunctionProtoType::ExtProtoInfo const&) const	/home/me/myApp/build/libLLVM.so		0x426ecbb	
6	clang::ASTContext::GetBuiltinType(unsigned int, clang::ASTContext::GetBuiltinTypeError&, unsigned int*) const	/home/me/myApp/build/libLLVM.so		0x4274243	
7	clang::Sema::LazilyCreateBuiltin(clang::IdentifierInfo*, unsigned int, clang::Scope*, bool, clang::SourceLocation)	/home/me/myApp/build/libLLVM.so		0x48baa24	
8	??	/home/me/myApp/build/libLLVM.so		0x49fde04	
9	clang::Sema::LookupName(clang::LookupResult&, clang::Scope*, bool)	/home/me/myApp/build/libLLVM.so		0x4a03d13	
10	clang::Sema::HandleDeclarator(clang::Scope*, clang::Declarator&, llvm::MutableArrayRef<clang::TemplateParameterList*>)	/home/me/myApp/build/libLLVM.so		0x48cb270	
11	clang::Sema::ActOnDeclarator(clang::Scope*, clang::Declarator&)	/home/me/myApp/build/libLLVM.so		0x48cb8f3	
12	clang::Parser::ParseDeclarationAfterDeclaratorAndAttributes(clang::Declarator&, clang::Parser::ParsedTemplateInfo const&)	/home/me/myApp/build/libLLVM.so		0x47196e1	
13	clang::Parser::ParseDeclGroup(clang::ParsingDeclSpec&, unsigned int, bool, clang::SourceLocation*, clang::Parser::ForRangeInit*)	/home/me/myApp/build/libLLVM.so		0x4725883	
14	clang::Parser::ParseDeclOrFunctionDefInternal(clang::Parser::ParsedAttributesWithRange&, clang::ParsingDeclSpec&, clang::AccessSpecifier)	/home/me/myApp/build/libLLVM.so		0x477563f	
15	clang::Parser::ParseDeclarationOrFunctionDefinition(clang::Parser::ParsedAttributesWithRange&, clang::ParsingDeclSpec*, clang::AccessSpecifier)	/home/me/myApp/build/libLLVM.so		0x4775d79	
16	clang::Parser::ParseExternalDeclaration(clang::Parser::ParsedAttributesWithRange&, clang::ParsingDeclSpec*)	/home/me/myApp/build/libLLVM.so		0x4779c77	
17	clang::Parser::ParseTopLevelDecl(clang::OpaquePtr<clang::DeclGroupRef>&)	/home/me/myApp/build/libLLVM.so		0x4779f48	
18	clang::ParseAST(clang::Sema&, bool, bool)	/home/me/myApp/build/libLLVM.so		0x470e49c	
19	clang::ASTFrontendAction::ExecuteAction()	/home/me/myApp/build/libLLVM.so		0x4671a57	
20	clang::CodeGenAction::ExecuteAction()	/home/me/myApp/build/libLLVM.so		0x456db42	
...	<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.

[agarny]

Nobody, really?...

[agarny]

Ok, I have spent some time googling around and... I have found some kind of a solution to my problem. I guess I should have mentioned that my Ubuntu box is, in fact, an Ubuntu virtual machine running within VirtualBox, and... since Qt 5 now requires OpenGL for any kind of application, well... that can cause problems depending on what you do and it certainly causes problems in my case (because of my use of LLVM). Anyway, the 'solution' consists of using indirect rendering, e.g.

$ LIBGL_ALWAYS_INDIRECT=1 ./myapp

Really not ideal, but at least it's now working fine. (Seriously, why on earth does Qt 5 forces you to use OpenGL in an application which doesn't actually make use of it?!)