Question

I am trying to build a small program and I have my own library libfoo. I have a camera class that is calling a static function from my Vector3 class (i.e. crossProduct). My camera class and Vector3 class compile ok and are built into libfoo. However when I am linking like so:

g++ -g -O2 -o test1 main.o -lfoo

I get this:

libfoo.so: undefined reference to 
foo::Vector3::dotProduct(foo::Vector3 const&, foo::Vector3 const&)

Now the function in Vector3.h is:

static Vector3 crossProduct(const Vector3 &v1, const Vector3 &v2); and is within the class definition... and it is defined in Vector3.cpp.

The program was fine until i called this static function inside Camera.cpp. In order to fix the problem I have to change the code in Vector3.cpp from what is in the header file to:

Vector3 Vector3::crossProduct(const Vector3 &v1, const Vector3 &v2) and it compiles, links, and runs OK.

The Vector3 class was written by someone else for a windows compiler, but I have moved it to Linux. Is this a g++ thing? Or bad code?

TIA.

Answer 1

It sounds like your vector3.cpp file originally had the following:

Vector3 crossProduct(const Vector3 &v1, const Vector3 &v2)
{
    ...
}

which you had to change to:

Vector3 Vector3::crossProduct(const Vector3 &v1, const Vector3 &v2)
{
    ...
}

The former is just defining a standalone function called crossProduct, whereas the latter is defining a member function of Vector3 called crossProduct. The latter is correct and what i m guessing to be the original code was incorrect.

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