[llvm-commits] [patch] fix linking of llvm-ld and lli with cmake

[Xerxes Rånby]

The problem:
Linking CXX executable ../../bin/llvm-ld
../../lib/libLLVMTransformUtils.a(LCSSA.cpp.o): In function 
`llvm::PredIteratorCache::~PredIteratorCache()':
LCSSA.cpp:(.text._ZN4llvm17PredIteratorCacheD1Ev[llvm::PredIteratorCache::~PredIteratorCache()]+0x11): 
undefined reference to `llvm::BumpPtrAllocator::~BumpPtrAllocator()'
...
../../lib/libLLVMAnalysis.a(DebugInfo.cpp.o): In function 
`llvm::DIDescriptor::dump() const':
DebugInfo.cpp:(.text+0x1e7e): undefined reference to 
`llvm::dwarf::TagString(unsigned int)'
...
Linking CXX executable ../../bin/lli
../../lib/libLLVMCodeGen.a(LLVMTargetMachine.cpp.o): In function 
`llvm::LLVMTargetMachine::addCommonCodeGenPasses(llvm::PassManagerBase&, 
llvm::CodeGenOpt::Level)':
LLVMTargetMachine.cpp:(.text+0x914): undefined reference to 
`llvm::createPrintFunctionPass(std::basic_string<char, 
std::char_traits<char>, std::allocator<char> > const&, 
llvm::raw_ostream*, bool)'
...
../../lib/libLLVMScalarOpts.a(CodeGenPrepare.cpp.o): In function 
`llvm::operator<<(llvm::BaseStream<std::basic_ostream<char, 
std::char_traits<char> > >&, llvm::ExtAddrMode const&)':
CodeGenPrepare.cpp:(.text+0x8a4): undefined reference to 
`llvm::ExtAddrMode::print(llvm::BaseStream<std::basic_ostream<char, 
std::char_traits<char> > >&) const'


This was quite odd since both libLLVMSupport.a and 
libLLVMTransformUtils.a got passed to the linker:


nm -A lib/*.a | c++filt | grep llvm::BumpPtrAllocator::~BumpPtrAllocator
..
lib/libLLVMSupport.a:Allocator.cpp.o:000004f6 T 
llvm::BumpPtrAllocator::~BumpPtrAllocator()
lib/libLLVMSupport.a:Allocator.cpp.o:00000508 T 
llvm::BumpPtrAllocator::~BumpPtrAllocator()
lib/libLLVMTransformUtils.a:LCSSA.cpp.o:         U 
llvm::BumpPtrAllocator::~BumpPtrAllocator()

by analysing the generated library .a archives it was clear the methods 
existed yet the linker tried to combine the librarys in the wrong order.
remember that linkers never look back to see if a new undefined symbol 
existed in a file it had allready processed.
thus if libLLVMSupport.a are passed to the linker before 
libLLVMTransformUtils.a then the linker will fail saying 
libLLVMTransformUtils.a have missing symbols.

The solution:
add target_link_libraries dependencies to the libraries so that cmake 
can figure out in what order the librarys should be passed to the linker.
This patch includes only whats needed to compleatly build llvm using cmake.

Cheers
Xerxes
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