what is macro

What are macro in c and how they are defined

Macros are a preprocessor directive that replaces the macro name with the code in the definition before compilation.

Code:

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#include <stdio>

#define myMacro printf("Hello World")

int main() {
  myMacro;

  return 0;
}

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There's about a dozen and a half reasons not to use macros, but that's how they are defined if you wished to use them. Consider using inline functions instead.

Quote:

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Originally Posted by SlyMaelstrom

Consider using inline functions instead.

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Hellow !!! this is a c forum not c++.

You can inline functions in C, genius.




(Right?)

Yes, that's correct, my bad. Either way, avoid macros.

Quote:

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Originally Posted by ahluka

You can inline functions in C, genius.
(Right?)

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No, I don't believe it's standard. Some compilers will take it, but I think it just ignores the keyword when you compile a C source.

EDIT: Off of a little research it seems inlining was fully accepted into the C99 standard, so it may actually be applied in C code. I'm not positive, though.

Ok I didn't know that.

EDIT: You must be able to. I swear I've done it before. Unless I tricked myself into thinking I was using C. Hmm.

EDIT2: You have to stop editing at the same time as me.

c99 does support function inlining. Unfortunately, many people use microsoft compilers which do not handle c99.

Gcc does, though - just compile with -std=c99.

Code:

---

#include <stdio.h>

#define SIX  1+5
#define NINE 8+1

int main ()
{
    printf("%d times %d equals %d", SIX, NINE, SIX*NINE);
    return 0;
}

---

> printf("%d times %d equals %d", SIX, NINE, SIX*NINE);
I wonder what this will print.
A demonstration of the precedence traps which can happen with macros no doubt :)