VC++ LNK2019 Error I can't seem to fix - c++

Question

So I was writing, as a small project, a stress test. Initially, to save time, I just plopped code in a header file. I decided to organise it a bit, and moved everything to a .cpp file and then wrote the header file, but VS2010 presented me with an LNK2019 that I can't seem to fix.
FSTRESS.cpp (Didn't include code, because I doubt it is relevant; ask if you need it)
FSTRESS.h
Main.cpp
The error:
error LNK2019: unresolved external symbol "public: static void __cdecl FSTRESS::Start(unsigned int,unsigned int,unsigned int)" (?Start#FSTRESS##SAXIII#Z) referenced in function _main C:\Programming\C++\FLOPS_Test\FSTRESS\FSTRESS\main.obj FSTRESS_Mk.II
Any ideas on why this is happening? I'm a bit of a C++ noob.
Thanks for any help :)

Answer 1

Your .cpp file is not defining the same classes as the ones you've declared in the .h, but creating different classes with the same name as those declared in the header. The correct way to do this is:
Header file:
class Foo
{
void Bar();
};
Implementation file:
void Foo::Bar()
{
// Do something
}
Alternately, you can declare the functions inline in the header file itself
class Foo
{
void Bar()
{
// Do something
}
};
In the latter case there's no need to create a separate implementation file. In fact, this is exactly what you're doing in fstress.cpp, but then you provide a duplicate declaration in fstress.h without actually defining that class anywhere.

Answer 2

So, you've actually got two separate definitions of the x86 and FSTRESS classes, one in the header file and one in the .cpp file. You're allowed to do that provided that the definitions are identical, but they aren't -- the one in the .cpp file has a bunch of inline code, which isn't there in the one in the header file. (Look up "one definition rule" for more information about this.)
What you actually want to do is this. Your header file is fine (or, at least, I don't see anything conspicuously wrong with it). The .cpp file should (1) #include the header file, and then (2) provide definitions for the member functions, looking like this:
static void FSTRESS::Start(unsigned aMode, unsigned aTest, unsigned aThreads) {
// code goes here
}
(When you have a source file and a corresponding header file, the source file should always #include the header file. This helps to make sure that if there's an inconsistency it gets caught tidily at compile time. I can't tell whether you were already doing that because the top of FSTRESS.cpp is invisible in your screen captures. It might have been better to post the code as text :-).)
As an aside, don't use names that begin with an underscore. A large portion of the space of such names is "reserved", meaning that the C++ implementation can use them internally and Bad Things can happen if your use clashes with its use. It's best just to avoid them all, because that way you don't have to remember what the exact rule is and neither does anyone else reading your code.

Answer 3

You can't just paste the contents of the class declaration with inlined code from the header file into the .cpp file and expect it to work. The implementation of FSTRESS::Start() needs to look morel like the following when you separate it from the class declaration:
void FSTRESS::Start(unsigned _aMode, unsigned _aTest, unsigned _aThreads)
{
//...
}
Also, you should #include "FSTRESS.h" in the FSTRESS.cpp file so there's exactly on declaration of the class that everyone uses (include the implementation bits in FSTRESS.cpp).