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MOVing between two memory addresses（6个答案）
Why can't MOV have both operands as memory locations? [closed]（1个答案）
关闭3个月前.

.686p 
.xmm
.model flat,c
.stack  4096

; include C libraries
includelib      msvcrtd
includelib      oldnames
includelib      legacy_stdio_definitions.lib

; imported functions
extrn   printf:near

.data ; initialized global vars
IntegerFormat   db  "The result is: %d",0dh,0ah,0
GlobWord      db "This is just a test",0dh,0ah,0
GlobFstC      dd "i"
GlobSecC      db "g"

.code
        
public  main

main proc
xor     eax, eax
xor     ecx, ecx
xor     ebx, ebx
mov     ecx, -1
mov     ebx, offset GlobWord

SwitchChars:
    inc     ecx
    movsx   eax, byte ptr [ebx + ecx]
    cmp     eax, 0
    je  Exit
    cmp     eax, GlobFstC
    jne     SwitchChars
    mov     byte ptr [ebx + ecx], GlobSecC 
    jmp     SwitchChars

Exit:
    movsx   eax, GlobWord
    push    eax    
    push    offset IntegerFormat
    call    printf  ; call printf(IntegerFormat, 3)
    add     esp, 8 
    xor     eax, eax
    ret
    main endp
    end

代码用于在字符串中的第二个字符中切换第一个字符，错误A2070“mov byte ptr [ebx + ecx]，GlobSecC”行上的“无效指令操作数”
有什么建议来修复/更好的方式来通过字符串在masm 32？