format ELF64 executable 3

segment readable executable

entry bitgamesasm

bitgamesasm:
    push rbp 
    mov rbp, rsp 
    
    mov rbx, rdi        ;load rbx with a
    mov rcx, rsi        ;load rcx with b
    xor rdx, rdx        ;initialize rdx(result) 0

countBits:
    ror rbx, 1            ;rotate right
    jnc bitIsZero       ;if C flag not set do not increment 
    inc rdx               ;if C flag set increment rdx

bitIsZero:
    loop countBits              

exit:
    mov rax, rdx        ; return value store in rax
    mov rsp, rbp 
    pop rbp 
    ret     

#include<stdio.h>

extern unsigned short bitgamesasm(int a, int b); 

int main(void){
    
    unsigned int a = 0;
    unsigned short b = 0;
    unsigned short result = 0;

    printf("Enter the number to check number of set bits: ");
    scanf("%d",&a);

    printf("Enter number of bits to check 32 or 64 : ");
    scanf("%hu", &b);

    result = bitgamesasm(a, b); 

    printf("For the number %d, number of set bits are %hu\n", a, result);
    return 0;
}
    

$ fasm bitgamesasm.fasm bitgamesasm.o
flat assembler  version 1.71.59  (16384 kilobytes memory)
2 passes, 151 bytes.

$ gcc bitgames.c bitgamesasm.o -o bitgames
/tmp/cckEcarp.o: In function `main':
bitgames.c.text+0x7c): undefined reference to `bitgamesasm'
collect2: error: ld returned 1 exit status