This code outputs T2, T4 for Visual Studio 2012 and 2008 and T1,T2,T3,T4 for gcc. What's the reason?
#include <iostream>
#define ABC
#define T1 defined(ABC)
#define T2 defined( ABC )
#define T3 defined(ABC )
#define T4 defined( ABC)
int main(int argc, char* argv[])
{
#if T1
std::cout<<"T1"<<std::endl;
#endif
#if T2
std::cout<<"T2"<<std::endl;
#endif
#if T3
std::cout<<"T3"<<std::endl;
#endif
#if T4
std::cout<<"T4"<<std::endl;
#endif
return 0;
}
Looking at conditional directives page. I've found that:
The defined directive can be used in an #if and an #elif directive, but nowhere else.
Changing your code to:
#include <iostream>
#define ABC
int main(int argc, char* argv[])
{
#if defined(ABC)
std::cout << "T1" << std::endl;
#endif
#if defined( ABC )
std::cout << "T2" << std::endl;
#endif
#if defined(ABC )
std::cout << "T3" << std::endl;
#endif
#if defined( ABC)
std::cout << "T4" << std::endl;
#endif
return 0;
}
Will produce T1,T2,T3,T4
output in VS 2013