firefox build broken under clang 3.3

[Dimitry Andric]

On Apr 30, 2013, at 18:34, Jan Beich <jbeich at tormail.org> wrote:
...
> The faulting function is lost within crash handler. If you build
> firefox with
> 
>  # use DEBUG_FLAGS or set STRIP to empty explicitly
>  CFLAGS += ${DEBUG_FLAGS}
>  DEBUG_FLAGS += -O0 -g
> 
> jaeger jit crash would look like
> 
> http://lists.freebsd.org/pipermail/freebsd-current/2013-April/041165.html

The firefox crash in that post was with -O2, so it is most likely not due to the vectorizer then.

In any case, I have not been able to reproduce that either.  I have browsed stackoverflow.com for about 5 minutes, clicking a whole bunch of random articles and links, and no problems whatsoever occurred.  That is with the default www/firefox port, which seems to be the released Firefox 20.0, at its default settings, on amd64.


> It doesn't happen on firefox23 with baseline jit[1] disabled via pref.
> A big change like zones (bug 759585) may have refactored code enough
> to not hit the clang bug. So, try either clang trunk or
> 
> http://trillian.chruetertee.ch/freebsd-gecko/changeset/1256/trunk/www/firefox/files/patch-clang33
> 
> The latter pessimizes inlining for clang 3.2 as well.
> 
> [1] baseline crashes in a different way
>    https://bugzilla.mozilla.org/show_bug.cgi?id=860867

I do not like the workaround in that Mozilla bug, since it simply disables the vectorizer.  I can understand that software must always ship tomorrow, but it would have been nicer to attempt to figure out what is incorrectly optimized, and why...


>> Rebuilding with debugging symbols provides no further insight, as that
>> seems to provide a work-around for whatever the root cause may be
>> (i.e. no more segfaults).
> 
> DEBUG enables compile-time diagnostics and strips any -O* from CFLAGS.

Indeed.  To work around this, use the following diff:

Index: Mk/bsd.port.mk
===================================================================
--- Mk/bsd.port.mk	(revision 316903)
+++ Mk/bsd.port.mk	(working copy)
@@ -1580,7 +1580,7 @@
 .if defined(WITH_DEBUG) && !defined(WITHOUT_DEBUG)
 STRIP_CMD=	${TRUE}
 DEBUG_FLAGS?=	-g
-CFLAGS:=		${CFLAGS:N-O*:N-fno-strict*} ${DEBUG_FLAGS}
+CFLAGS:=		${CFLAGS} ${DEBUG_FLAGS}
 .endif
 
 .if defined(NOPORTDOCS)