Of course, there is nothing wrong with using old software. Except the unfixed bugs. And missing functionality.
I'll skip the problems with .fill, .string or .ascii directives, and with aliases for some instructions. The biggest surprise were LOOP and LOOPNE.
I seems that LOOP/LOOPNE is supported. And it even works in small programs. But, when a bigger code comes into play, it came out that the loop's argument is calculated incorrectly. Let's look at the example:
Source (AT&T syntax):
(gdb) x/10i $eip
0xe318a <jump_f09d4>: mov (%edi),%al
0xe318c <jump_f09d4+2>: mov (%eax,%esi,1),%bl
0xe318f <jump_f09d4+5>: mov %bl,(%edi)
0xe3191 <jump_f09d4+7>: add $0x1,%edi
0xe3194 <jump_f09d4+10>: loop 0xe3187 <jump_f09bb+26>
0xe3196 <jump_f09d4+12>: jmp 0xe31cb <jump_f0a0b>
As one can see, the LOOP in the output should jump to 0xe318a, but it jumps to 0xe3187 - 3 bytes too early. And what's interesting, it was always 3 bytes. It look like the assembler started to think that the LOOP instruction is not made of opcode + 1 byte argument (2 bytes total), but, it thought it was opcode + 4 byte argument (5 bytes), and it used eip+5 as the jump origin, instead of eip+2 as it should - 3 byte difference. LOOPNE behave the same way. LOOPE we didn't use ;>
The LOOP problem was solved by changing the LOOP instruction to the following equal code:
LOOPNE was replaced by this:
And everything suddenly started to work.
I hope Apple will upgrade it's assembler some day ;D