I wrote a C extension file program where my function is declared with C langage with parameters and writen in ASM langage: int MyFunc(int param1, int param2) { #asm ... ... #endasm } From other files, the call is working but I have WARNING in compilation of my assembly file on param1 and param2 because I don't use them directly but I use register R4 to R7. The program is working but I don't understand how can I write the program to don't have any warning.