Compiling error when -std=gnu99 and inline function is used

Question

The following code:

#include 
inline int myfunc (int x) {
    return x+3;
}

int main () {

    printf(\"%d\", myfunc(2));
    return 0;
}
         


        

Answer 1

You should declare 'myfunc' before define it. For example this code can be compiled with -std=gnu99 option:

#include 

int myfunc(int);

inline int myfunc (int x) {
    return x+3;
}

int main () {

    printf("%d", myfunc(2));
    return 0;
}

UPDATED

Actually, regarding to the C standard inline keyword is just a suggestion to the C compiler. But compiler can choose not to inline. So it can do its own way, therefore.

In your example you can use function declaration as I showed above - or you can add optimization flag '-O3' (tested on linux gcc) and above - in this case your source code will compiled without extra-declaration.

UPDATED

Here you can find deeper explanation: https://blogs.oracle.com/dew/entry/c99_inline_function