A major drawback of Macro in C/C++ is that the arguments are strongly typed checked i.e. a macro can operate on different types of variables(like char, int ,double,..) without type checking.
// C program to illustrate macro function. #include<stdio.h> #define INC(P) ++P int main() { char *p = "Geeks"; int x = 10; printf("%s ", INC(p)); printf("%d", INC(x)); return 0; } |
Output:
eeks 11
Therefore we avoid to use Macro. But after the implementation of C11 standard in C programming, we can use Macro with the help of a new keyword i.e. “_Generic”. We can define MACRO for the different types of data types. For example, the following macro INC(x) translates to INCl(x), INC(x) or INCf(x) depending on the type of x:
#define INC(x) _Generic((x), long double: INCl,
default: INC,
float: INCf)(x)
Example:-
// C program to illustrate macro function. #include <stdio.h> int main(void) { // _Generic keyword acts as a switch that chooses // operation based on data type of argument. printf("%d
", _Generic( 1.0L, float:1, double:2, long double:3, default:0)); printf("%d
", _Generic( 1L, float:1, double:2, long double:3, default:0)); printf("%d
", _Generic( 1.0L, float:1, double:2, long double:3)); return 0; } |
Output:
Note: If you are running C11 compiler then the below mentioned output will be come.
3 0 3
// C program to illustrate macro function. #include <stdio.h> #define geeks(T) _Generic( (T), char: 1, int: 2, long: 3, default: 0) int main(void) { // char returns ASCII value which is int type. printf("%d
", geeks('A')); // Here A is a string. printf("%d",geeks("A")); return 0; } |
Output:
2 0
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