Source code in the x86 programming language

format PE64 console
entry start

    include 'win64a.inc'

section '.text' code readable executable

    start:
        stdcall dotProduct, vA, vB
        invoke printf, msg_num, rax
        
        stdcall dotProduct, vA, vC
        invoke printf, msg_num, rax
        
        invoke ExitProcess, 0
        
    proc dotProduct vectorA, vectorB
        mov rax, [rcx]
        cmp rax, [rdx]
        je .calculate
        
        invoke printf, msg_sizeMismatch
        mov rax, 0
        ret
        
        .calculate:
        mov r8, rcx
        add r8, 8
        mov r9, rdx
        add r9, 8
        mov rcx, rax
        mov rax, 0
        mov rdx, 0
        
        .next:
            mov rbx, [r9]
            imul rbx, [r8]
            add rax, rbx
            add r8, 8
            add r9, 8
            loop .next
        
        ret
    endp

section '.data' data readable

    msg_num db "%d", 0x0D, 0x0A, 0
    msg_sizeMismatch db "Size mismatch; can't calculate.", 0x0D, 0x0A, 0
    
    struc Vector [symbols] {
        common
        .length dq (.end - .symbols) / 8
        .symbols dq symbols
        .end:
    }
    
    vA Vector 1, 3, -5
    vB Vector 4, -2, -1
    vC Vector 7, 2, 9, 0
    
section '.idata' import data readable writeable

    library kernel32, 'KERNEL32.DLL',\
            msvcrt, 'MSVCRT.DLL'

    include 'api/kernel32.inc'

    import  msvcrt,\
            printf, 'printf'

3
Size mismatch; can't calculate.
0