Re: [Qemu-devel] qemu vs gcc4

[Rob Landley]

On Friday 20 October 2006 2:53 pm, K. Richard Pixley wrote:
> Could someone please explain the issue with gcc4, please?  Or point me 
> to an existing explanation?
> 
> I mean, I understand that qemu is believed to be building incorrectly 
> with gcc4.  But what is the failure mode folks have been seeing?  And 
> what's being done about it or what needs to be done about it?  Is this 
> an issue for all targets or is it x86 specific?

There's a patch to fix it in http://busybox.net/downloads/qemu (which works 
for 0.8.0 through 0.8.2, dunno about current cvs).  This is a collection of 
four different patches I got from a gentoo web page via google.

Basically, gcc changed in a way that broke qemu.  There's been an open bug 
report in gcc ever since, but the GCC developers really aren't interested in 
backwards compatability.  (Heck, gcc 4.0 breaks building bash 2.05b).  The 
qemu developers aren't interested in applying ugly patches to support gcc 4.x 
until gcc 3.x becomes so obsolete nobody ships it anymore.  (And considering 
that there are still some niche embedded boards that have hacked up versions 
of gcc 2.95 targeting them and nothing else, I wouldn't be surprised if in 
five years we have your main compiler and the compiler to build qemu, ala 
kgcc under Red Hat 7.  *shrug*)

I was pondered trying to get tcc to build qemu, and even made a mercurial copy 
of CVS and started collecting old patches from the list (since CVS hadn't had 
a single patch checked into it in eight months and there were other old 
patches from a full year ago which I needed to apply before the thing would 
work on Ubuntu 6.06).  But Fabrice showed back up on tuesday and checked in a 
patch, and now I've got a fork that's out of sync with mainline.  Since I 
have no desire to be in Fabrice's way if he still has any interest in the 
project, I've mothballed my fork and moved on to other things...

The current state of TCC trying to build qemu-0.8.2 is that it blows up on the 
very first file.  Just getting it to compile the full source (let alone 
actually work) seems like a significant undertaking, but I was trying it as a 
learning experience so who knows how much work it actually is.  Might be 
simple if you know what you're doing...

Rob
-- 
"Perfection is reached, not when there is no longer anything to add, but
when there is no longer anything to take away." - Antoine de Saint-Exupery