问题
I am having trouble with pointing to a address and write in my case a variable of byte in size. This gives me the error \"error: invalid effective address\":
mov byte[AX], byte 0x0
After some trail and error i tested the same but with EAX. This compiles just fine:
mov byte[EAX], byte 0x0
What am I missing here?
回答1:
[AX] is an invalid memory operand specification.
The valid 16-bit ones are:
[constant]
[BX]
[SI]
[DI]
[BX+constant]
[BP+constant]
[SI+constant]
[DI+constant]
[BX+SI]
[BX+DI]
[BP+SI]
[BP+DI]
[BX+SI+constant]
[BX+DI+constant]
[BP+SI+constant]
[BP+DI+constant]
[BP] is formally invalid, but many assemblers will quietly convert it into [BP+0].
See the CPU manual for memory operand encodings and the ModR/M and SIB bytes.
来源：https://stackoverflow.com/questions/12474010/nasm-x86-16-bit-addressing-modes