[LLVMdev] Error while linking LLVM files

Eli Friedman eli.friedman at gmail.com
Tue Nov 6 09:35:33 PST 2012

On Tue, Nov 6, 2012 at 6:38 AM, Wojciech DaniƂo
<wojtek.danilo.ml at gmail.com> wrote:
> Hi!
> I'm trying to learn LLVM and I want to compile the Kaleidoscope compiler.
> according to:
> http://llvm.org/docs/tutorial/LangImpl3.html
> I'm compiling it with:
> clang++ -g -O3 test.cpp `llvm-config --cppflags --ldflags --libs core` -o
> toy
> and it indeed works.
> The problem is that when using eclipse it forces me to divide the
> compilation into two steps:
> g++ -O0 -g3 -Wall -c -fmessage-length=0 `llvm-config --cppflags --ldflags
> --libs core` -MMD -MP -MF"src/lunac.d" -MT"src/lunac.d" -o "src/test.o"
> "../src/test.cpp"
> (which compiles fine)
> and:
> Invoking: Cross G++ Linker
> g++ `llvm-config --cppflags --ldflags --libs core` -o "test"  ./src/test.o
> which gives me error:
> ./src/test.o: In function `NumberExprAST::Codegen()':
> /home/wdanilo/dev/lunac/Debug/../src/test.cpp:358: undefined reference to
> `llvm::APFloat::APFloat(double)'
> /home/wdanilo/dev/lunac/Debug/../src/test.cpp:358: undefined reference to
> `llvm::getGlobalContext()'
> /home/wdanilo/dev/lunac/Debug/../src/test.cpp:358: undefined reference to
> `llvm::ConstantFP::get(llvm::LLVMContext&, llvm::APFloat const&)'
> [...]
> Why Linker is not working with these flags? How can I fix it?

When you're passing arguments to the linker, the order matters.  Try
reordering the command-line so test.o comes first.


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