GCC 4.6.3 compilation bug for ARM

[William King]

There appears to be an RTL level compilation bug that optimizes out required lines of code. Specifically this version of GCC optimizes out a required strcasecmp in the FreeSWITCH code which causes all new call negotiations to fail.

Filed upstream against GCC here:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61509

More specific logs and details here:
http://quentusrex.com/freeswitch-raspberrypi-gcc-compiler-bug.html

The problem did not appear to exist on 4.7.2, or at least not in the same way.

[William King (quentusrex)]

uname -a:
Linux raspberrypi 3.10.25+ #622 PREEMPT Fri Jan 3 18:41:00 GMT 2014 armv6l GNU/Linux

[peter green (plugwash)]

It doesn't entirely surprise me that gcc has bugs on armv6 hardfloat since afaict it's a little used configuration, nor does it surprise me that 4.7 fixes some bugs that were in 4.6

having said that I don't think there is much we can do from the raspbian end. Changing the default compiler may fix some bugs but it may cause others and so it's out of the question for a stable release of raspbian (and probablly even for a testing release of raspbian but that's kinda academic since raspbian jessie is already on 4.8 and will probablly be on 4.9 in the not too distant future)

Theres also the problem that even if a targetted fix was available we don't have any resources to review it. So we would likely only accept it if it had been signed off by some reasonablly prominent gcc person. Given that the 4.6 branch has been abandoned upstream that seems unlikely.

if the issue related to an application that was in raspbian we could alter the packaging for that one application to use a non-default compiler but afaict freeswitch is not in debian or raspbian.

[Diederik (didi-debian)]

Wheezy has gcc-4.7 (and gcc-4.8 via raspberrypi.org repo).

Furthermore it looks like the gcc developers have no intention of fixing 4.6 (or 4.7 even).

Do you still want to keep this bug open?

(Impressive triaging work btw)

[William King (quentusrex)]

Since the release of jessie, I don't think too many folks would hit this
bug in the field. I do wish that the wheezy gcc default version could be
set to 4.7, but I've already moved my projects to jessie.

Thanks.

-William

On 1/12/16 11:48 AM, Diederik wrote:
> Wheezy has gcc-4.7 (and gcc-4.8 via raspberrypi.org repo).
>
> Furthermore it looks like the gcc developers have no intention of fixing
> 4.6 (or 4.7 even).
>
> Do you still want to keep this bug open?
>
> (Impressive triaging work btw)
>
> ** Changed in: raspbian
> Status: New => Incomplete
>

[peter green (plugwash)]

If someone puts the effort in to track down the gcc commit that fixed it and provide a backport then I may consider applying it but since I don't think that is likely to happen "won't fix" seems like the appropriate status for this bug.