Fixing the "fnstsw" compile bug without using --disable-asm

no-reply@allegro.cc (Bernhard Rosenkraenzer) — Sat, 04 Oct 2008 20:27:29 +0000

Hi,
I've seen various posts about the "fnstsw" compile bug - always with a reply stating --disable-asm or --enable-asm=no fixes it.

While that does fix it, it also disables some optimizations -- there is a better fix.

The problem is caused by the use of the asm statement

fnstsw %eax

That used to work with old versions of binutils, current binutils versions (correctly) reject it as invalid because it uses a 16 bit operation on a 32 bit register.

The correct fix is to work on the 16 bit version of the register instead:

fnstsw %ax

I'm attaching a patch that fixes this.

no-reply@allegro.cc (kazzmir) — Sat, 04 Oct 2008 22:13:23 +0000

Its normal to disable asm because the C code is just as fast these days.

If no other Allegro dev pushes this through and no one else disagrees then I'll apply it for you.

no-reply@allegro.cc (Evert) — Sat, 04 Oct 2008 23:10:33 +0000

No reason to not apply it.
It does mean that we should output 4.4 at least, maybe 4.2.3 (with just minor fixes like this) as well.