[RESOLVED] #define vs. int, double, etc

[CodingFreak]

Why use #define preprocessor directive to declare constants when they can be declared with int = or double =

What advantage does #define have?

[CodingFreak]

#define can tell the compiler not to compile the same header two or more times.
Reference: http://www.learncpp.com/cpp-tutorial...-preprocessor/

[JohnW@Wessex]

What advantage does #define have?

Not a lot.
There are very few instances in which I find #define to be necessary.
Code in macros are hard to debug.
Macros do not respect namespaces and struct/class definitions.

e.g.
Anyone who has tried to define a member function called 'GetMessage' under Windows will have come across the error message stating that 'GetMessageA' was not defined.

[ninja9578]

#define has uses other than defining constants. It's very useful for manipulating things where inline functions aren't capable of doing what you want, or using compiler specific optimizations on code that may be compiled on multiple compilers.

#ifdef __GNUC__
    #if ((__GNUC__ * 100 + __GNUC_MINOR__) >= 403)
	   #define HOTSPOT __attribute__ ((hot))
    #else
	   #define HOTSPOT
    #endif
#else
    #define HOTSPOT
#endif

void methodThatGetsCalledAlot(void) HOTSPOT;  //can create dramatic increase in performance due to code localization
void methodThatGetsCalledAlot(void){
    //code
}