[mythtv] Profile builds and debug code

[Lawrence Rust]

On Sun, 2012-03-11 at 09:31 -0400, Daniel Kristjansson wrote:
> On Sat, 2012-03-10 at 18:57 +0100, Lawrence Rust wrote:
> > I've been profiling some Myth functions using the --compile-type=profile
> > configure option and noticed that doing so results in Myth linking
> > against debug builds of Qt libs.  This is selected in settings.pro:
> > 
> > profile:CONFIG += debug
> > 
> > I was wondering what the reason for this was?
> 
> This is the build most distros use so this is what performance the
> users will see. Anyway, all we really want is the debugging symbols
> so the profile is human readable. It would be preferable if the qt
> libraries were still compiled for performance.

It's because the profile build is now the standard for Myth that I asked
this question.  The debug build of Qt has a lot of additional runtime
checks and is not optimised.  So Myth will suffer a memory overhead and
performance penalty.  That doesn't sound good.  What's more a distro
will now have to distribute the Qt -dbg packages just for Myth.

I don't think that we need the Qt symbols in a release(profile) build; a
backtrace through Qt isn't useful to anyone but developers.  If the
symbols are required, many distros provide this as a separate package to
the optimised build.

-- 
Lawrence