197039 - Keep Windows gcc xptc code separate from unix

Status: RESOLVED WONTFIX

(Core :: XPCOM, defect)

Description

[tenthumbs]

The fix for bug 134113 has Windows using part of the unix gcc xptcall code.
That's nice but I have bug 195736 which proposes using the regparm calling
convention for internal functions. This is (perhaps small) performance win on
Linux but I have no idea if it even works on Windows. I see that there was some
problem with using xptcstubs, maybe the regparm stuff was part of it.

In any event I propose keeping Windows separate, at least until there's more
testing.

Patch upcoming.

Comment 1

[tenthumbs]

Attachment: patch

Patches Makefile.in and creates xptcinvoke_gcc_x86_win32.cpp.

Comment 2

[hacker formerly known as [e-mail]]

-> xptcall

Comment 3

[hacker formerly known as [e-mail]]

dbradley specifically asked that we reuse the xptcinvoke_gcc_x86 code.  You'll
have to take this up with him.  How is the gcc_x86 code going to be reusable for
other OSes (as alluded to in bug I'm too tired to lookup) if Linux specific bits
get added?
  

Comment 4

[David Bradley]

I need to take a look at this, get it straight in my head, and see if I can come
up with some decent alternatives. I just hate duplicating all that code.

Comment 5

[David Bradley]

Is this still an issue? Bug 195736 has been fixed, so does this still need to be
separated?

Comment 6

[tenthumbs]

Yes, I still think it's far better to separate this. You're basically 
trying to mix two completely different OS's together just because they 
share a compiler. I know I once said that was a good idea but not I 
think I was, at least partially, wrong. There are just too many 
differences.

Also, I'm a believer in one of K&R's rubrics on good programming 
practice, namely that ifdefs should be avoided. As they point out, if 
you have N ifdefs you have 2^N different states so you have exponential 
complexity. That's a big maintenance problem. To support Windows, two 
ifdefs were introduced. I don't see how a factor of 4 in complexity is a 
win.

Comment 7

[David Bradley]

Conversely by separating we'll be duplicating a lot of code that someone will
forget to keep in sync, that's also a big maintenance problem. If we were
#ifdef'ing large sections of this file based on OS, then I'd agree. These are
relatively small tweaks and the bulk of the code is constant. At best it's a
wash IMO. Adding another file needs some kind of payoff, because that will add
another state for the build system to deal with.