Question

I’ve created a structure in a header file as follows:

typedef struct
{
    GLfloat lgtR, lgtG, lgtB, lgtA;
    GLfloat x, y, z;
    bool islight;
    GLfloat width, height, depth;
    GLenum lightn;
    particle prt;
    int maxprt;
} emitter;

which works without a problem.

However, in that particular header file, I want to declare a global emitter that I can use in all the functions and isn’t part of the main source file:

// header.h global declaration

emmiter currentEmit;

GLvoid glSetEmitter(emitter emitter)
{
    currentEmit = emitter;
}

However, when I do try this, I get a whole lot of “error C2228: left of ‘.variable’ must have class/struct/union, so I’m assuming it’s not declaring my structure here at all.

Is there a way to declare that structure globally within a header file, and if so, is there also a way to keep it from being part of the other .cpp files as well?

Answer 1

emitter is not the same as emmiter.

Also, since this is C++ – just write struct {}; directly, there’s no need for a typedef.

Your whole header is wrong, and will give multiple definitions if included in multiple translation units:

// header.h global declaration
extern emitter currentEmit;   // <-- note extern

inline GLvoid glSetEmitter(emitter emitter)  // <-- note inline
{
    currentEmit = emitter;
}

currentEmit needs to be defined in a single implementation file, not a header. The function needs to be inline so it’s not defined by all TU.

Last thing: pass the parameter by const reference:

inline GLvoid glSetEmitter(const emitter& emitter)  // <-- note inline
{
    currentEmit = emitter;
}

Otherwise an unnecessary copy will be created.