由于汇编语言中的mul命令未设置Zf

Question

I am using masm615 assembler and textpad as an editor. I am writing 32 bit assembly program. In the program I am trying to set zero flag as a result of mul instruction but it is not working. Can anyone tell me why the zero flag is clear while the result in eax register is zero. I am trying the following code

    include irvine32.inc
    .data
    .code
    main proc
    xor eax,eax
    call dumpregs
    xor ebx,ebx
    call dumpregs
    mov eax,2
    call dumpregs
    mov ebx,3
    call dumpregs
    sub eax,2
    call dumpregs
    mul ebx
    call dumpregs
    exit
    main endp
    end main

Answer 1

In the program i am trying to set zero flag as a result of mul instruction

The mul instruction does not affect the zero flag, see Intel® 64 and IA-32 Architectures Software Developer's Manual Volume 2 page 3-594:

MUL—Unsigned Multiply

...

Flags Affected

The OF and CF flags are set to 0 if the upper half of the result is 0; otherwise, they are set to 1. The SF, ZF, AF, and PF flags are undefined.

If in doubt, always check the instruction documentation in the developers manual. Not all instructions affect the flags which one might expect.