extern declaration and function definition both in the same file

Question

I was just browsing through gcc source files. In gcc.c, I found something like

extern int main (int, char **);

int
main (int argc, cha         


        

Answer 1

In a function declaration, extern simply declares that the function has external linkage, which is the default; the extern keyword is utterly useless in this context, and the effect is identical to a normal declaration/prototype without the extern keyword.