why no error message when alias function with different prototype?

Question

test.c
void __f () { /* Do something. */; }
int f (int) __attribute__ ((weak, alias ("__f")));

test.h
void f ();


main.c
//call f
f();

the __f() and alias f() has different prototype.

use build tools gcc-arm-none-eabi-4_9, no error or warning messages. why,and what will happened?