In C ++, what you observe in a quick internet search is the guideline that only ".h" files should be included. A sample of this can be seen here and especially here .
In Visual Studio, adding only ".h" with #include ... is not a problem as long as the ".cpp" deployment files are included in the project. This ensures that they will be compiled and there will be a valid reference for the methods of the class. However, this does not seem to be the case for GCC (g ++). See the code below:
Mt.h
#ifndef MT_H
#define MT_H
namespace Subsistema {
class Mt {
public:
int soma(int i, int d);
};
}
#endif
Mt.cpp
#include "Mt.h"
namespace Subsistema {
int Mt::soma(int i, int d) {
return i + d;
}
}
main.cpp
#include <iostream>
#include "Mt.h"
int main(int argc, char *argv[]){
Subsistema::Mt * t = new Subsistema::Mt();
std::cout << "Soma: " << t->soma(3, 5) << std::endl;
delete t;
return 0;
}
The above code will compile perfectly in Visual Studio even though there is no #include Mt.cpp , as long as it is included in the project. But it will NOT do it in g ++ , with the following error message:
/tmp/ccQVvF4r.o: In function 'main':
main.cpp: 7: undefined reference to 'Subsystem :: Mt :: soma (int, int)'
collect2: error: ld returned 1 exit status
This error could easily be resolved by adding the #ifdef __GNUC__ macro, as follows:
#ifndef MT_H
#define MT_H
namespace Subsistema {
class Mt {
public:
int soma(int i, int d);
};
}
#ifdef __GNUC__
#include "Mt.cpp"
#endif
#endif
But the point is, this is a solution, but is it the right solution (best practice) for the situation? I need a solution, as far as possible, independent of the compiler used.
NOTE: This question is closely related to How to include header and cpp without resulting in LNK2005 error in Visual Studio