Persistent undefined reference - c++

Question

I am having a persistent undefined symbol error in Eclipse on MAC OS X. I can't figure
out the source of the error.
The error occurs according to the compiler when I try to use GA_Operations and gaAlgorithm->run_algorithm..... below:
int Application::execute_Algorithm()
{
if (this->GA_On)
{
GA_Operations *gaAlgorithm = new GA_Operations();
gaAlgorithm->run_algorithm(blocksSequence, bins);
}
else
{
packingAlgorithm->run_algorithm(blocksSequence, bins); return 0;
} //
return 0;
}
The error showing is:
Undefined symbols for architecture x86_64:
"binproject::GA_Operations::run_algorithm(binproject::Blocks_Sequence&, binproject::BinContainer&)", referenced from:
binproject::Application::execute_Algorithm() in Application.o
"binproject::GA_Operations::GA_Operations()", referenced from:
binproject::Application::execute_Algorithm() in Application.o
And the declaration is:
class GA_Operations {
public:
GA_Operations();
~GA_Operations();
//call from main application to execute algorithm
void run_algorithm(Blocks_Sequence &b_seq, BinContainer &container);
...
};
It also throws a similar error anytime I try to define a declared function in the
implementation (CPP) file.
Any ideas? This only seems to happen with this class.
Also, I apologize if there is a problem with the code indenting, I'm

Answer 1

The error you are showing is a linker error. This means that the compiler thinks something exists, but the linker can't find where you've defined (not declared) it. Somewhere you need something like this:
GA_Operations::GA_Operations()
{
// construct
}
void GA_Operations::run_algorithm(Blocks_Sequence &b_seq, BinContainer &container)
{
// stuff
}
Do you have that anywhere? If so, is it in the same file that Application::execute_Algorithm is in?
If it isn't, where is it? How are you compiling your whole program together so the stuff in these different files ends up in the same executable?
I'm not at all sure how to make Eclipse do what you need. I know it's possible, but I'm for familiar with pure command-line tools. You need to tell Eclipse that the .cpp file that contains the above definitions is part of your project and should be compiled and linked into the executable you're created.

Answer 2

Turns out this was an issue with linker settings. I turned on generating makefiles automatically and the problem resolved itself.