undefined reference to

[Ceset]

hi guys

i was working on a error manager and come across with a problem

i declare this at defines.h and it is global
extern std::string fgeError;

core.h includes defines.h and includes.h. also defines.h includes includes.h

and i use this fgeError at core.cpp. this function is defined in a namespace

void Logger(std::string message)
{
    fgeError.clear();
    fgeError.append(message.c_str());
    fgeError.append(" - ");
    fgeError.append(SDL_GetError());
}

all i want is to make a string which holds last error. i use SDL2 and the compiler gives me

undefined reference to `fgeError'

error

sorry i cant post all the codes, it is so large any info you need will be sent just tell me

[coder777]

the extern keyword tells the compiler that the object is defined somewhere else, hence you need to define it somewhere else (core.cpp) like so:
std::string fgeError; // Note: without extern

[Beware threading when using globals]

[Ceset]

thx