Consider this sequence: 0041301E 33 D2 xor edx, edx 00413020 83 E8 02 sub eax, 2 00413023 74 01 jz loc_00413026 00413025 4A

Consider this sequence: 0041301E 33 D2 xor edx, edx 00413020 83 E8 02 sub eax, 2 00413023 74 01 jz loc_00413026 00413025 4A dec edx 00413026 ... Without a single-byte int 3, a break on dec edx will mess up everything if that branch is not taken.