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assemblyx86att

CMP in x86 with parentheses and address

I have the following line in x86 Assembly language that I don't know what it does...

cmp %eax,0x80498d4(,%ebx,4)

I know it's comparing the two halves of the statement but I don't know what the address does in it and what the parentheses do either. Some clarification would be much appreciated!

Solution

  • In AT&T syntax this form represents

    OFFSET(BASE REGISTER, INDEX REGISTER, INDEX SCALE)

    so the address represented is the value of BASE REGISTER (if present) + INDEX * SCALE (if present) + OFFSET, so

    EBX*4 + 0x80498d4 in your case.