C: Which is the difference between inline function and macro function ?

Question

Can someone help me with the example when to use normal function calling and when pointer function calling. What was the reason for introducing pointer function calling in C?

Answer 1

Difference between inline function and macro function is same as difference between function and macro.

To get gyst of difference, try the following code.

#define FUN(a) a+a

int fun(int a)
{
 return a+a;
}

int main()
{
 int a=1;
 FUN(a++);
 fun(a++);
 return 0;
}

In FUN(a++), a will be incremented as many times as it is being used. In fun(a++), it will be incremented once. So, any operation on parameter will be repeated in macro multiple times.

You can debug through inline functions, but not through MACRO.

You can specify the type of parameter in inline function, but not in MACRO.

Using MACRO as function is not recommended. In such cases, do not expect anything good from the debugger.

Answer 2

Check the following WiKi Links http://en.wikipedia.org/wiki/Inline_function#Comparison_with_macros

In Summary -
Inline replaces a call to a function with the body of the function in every place that the function is called however Compilers are not obligated to respect this request. (user always_inline with gcc to force the inline operation)

A macro on the other hand, is expanded by the preprocessor before compilation, so it's just like text substitution, also macros are not type checked where as inline functions are.