Benefits of using Macro

What is the Macro?
If you write as “#define” in your code, that is “Macro” .
Macro will handle by the preprocessor.
You can think Macro as a method to replace the String which appears in you code..
pros:
– run faster than writing as function
cons:
– occupy memories
concepts:
– there is no the concept of pointer in macro.
just “replacing the string”
An question:
What is the output of the following code?
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#define macro_to_func(pp) ({printf("in Macro ...\n"); minus ;})
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​
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void do_something(int *a, int *b){
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    printf("do_something\n");
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    int c;
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    c = *a + *b;
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    printf("do_something %d \n", c);
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}
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​
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int minus(int *a, int *b){
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    printf("minus\n");
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    int c;
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    c = *a - *b +1;
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    printf("minus a = %d \n", *a);
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    printf("minus b = %d \n", *b);
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    printf("minus %d \n", c);
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    return c;
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}
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​
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int main()
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{
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    int (*do_something)(int* c, int* d);
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    //printf("fptr 1 do_something %p\n", &do_something);
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​
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    int m = -1;
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    int n = 7;
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​
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    printf("do_something = macro_to_func\n");
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    do_something = macro_to_func(pp);
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    //printf("fptr minus %p\n", &minus);
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    //printf("fptr 2 do_something %p\n", &do_something);
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    if(do_something){
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        printf("in IF!!\n");
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        do_something(&m, &n); --------------------------->???
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    }
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    return 0;
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}
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Answer:
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do_something = macro_to_func
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in Macro …
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in IF!!
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minus
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minus a = -1
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minus b = 7
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minus -7
Copied!

Explanation:
“int (*do_something)” is a local function pointer.
In the macro, the macro_to_func will be replaced as “minus”, but do_something !!!

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