Hi, I'm checking some of my old OS code and while trying to get a working development environment going on my Mac I encountered this error:

"Invalid use of symbol"

Something I do not get if I assembly with the older 1.60 version.

The line in question looks like this:


and it seems to be the divide by 2 part it doesn't like.

I haven't done any assembly programming in years - but this doesn't look pretty Anybody have idea on why it did work at one point, and why it doesn't anymore?

Is there somewhere I could get a summary of changes affecting syntax from 1.60 and forward?

bubach

Yes. This is soo wrong. What was actually compiled is "mov [idt_list+eax], edi". This bug has been eliminated in 1.66 and it seems to be summarized under "many other small bugs fixed".

WHATSNEW.TXT

you must mean "mov [idt_list+ecx], edi"? so before the bug fixes it just ignored the divide by 2?

No, it really does give "mov [idt_list+eax],edi"

bubach
No. I mean eax. My first thought was that fasm just divides the native register number (like you know: ecx/2 = eax, esi/2 = ebx, etc.) But in a couple of superficial tests it always took eax.

wow. must have been close to miraculous that my old code would run without errors in that case. probably helped that the line above was:

Hm, I have another strange thing going in my bootsector. It seems as it no longer assembles this



into "EB 3C 90" but instead into "E9 3C 00 90"... sigh. something changed with near jumps, or could this be a bug in the hacked OS X version of fasm?

bubach
The keyword near enforces a long encoding of a relative jump. The keyword short enforces a short encoding of a relative jump. If you specify neither of those the short encoding is used unless it's not possible.

See the documentation for explanation of keywords.

That code is untouched since like, 2003. But yeah, okey - probably another thing changed since 1.60. Thanks!

Argh, I also had to deal with this issue:
http://board.flatassembler.net/topic.php?t=3286

No way to avoid it any longer. Well, moving the codebase down below 0x10000 to maybe 0x8000 should do it. I hope.

bubach
I can't see any real issues with staying above 0x10000. As for jumping into protected 32-bit mode you just do jmp fword 0x08:do_pmode . As for data shared across both modes, you just define two labels for each shared variable. There are possibilities to make neat and easy-to-use macros for that, so that there's no visual difference to your previous code.