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Re: [MPlayer-dev-eng] [PATCH v2] configure: Avoid eh_frame bloat in release builds




On Sat, Feb 13, 2016 at 05:40:34PM +0200, Lauri Kasanen wrote:
> On Sat, 13 Feb 2016 16:26:42 +0100
> Reimar Döffinger <Reimar.Doeffinger@xxxxxx> wrote:
> 
> > On Sat, Feb 13, 2016 at 05:03:17PM +0200, Lauri Kasanen wrote:
> > > Hi,
> > > 
> > > This patch reduces both mplayer and mencoder size by 1mb, or 6%. The
> > > eh_frame sections are mainly used for C++ exceptions and accurate
> > > debugging, neither of which is desired in a C program and a release
> > > build.
> > 
> > To the best of my information, at the very least
> > -fno-asynchronous-unwind-tables has no effect on debuggability
> > if debug info is present.
> > Thus is it should be set always.
> > Did you check whether -fno-unwind-tables has any effect at all?
> > I think this one is potentially not completely safe (we do have
> > C++ code) and it would be better to not add it unless it really
> > provides a significant benefit.
> 
> -fno-async provides the majority of the size benefit indeed, the
> difference was just bytes. Attaching v2.

I also suspect, as we are checking it to work anyway, that this
shouldn't be gnu only.
Seems reasonable to believe that other compilers might have the
same option.

> The few C++ files in mplayer and ffmpeg do not use exceptions
> (incidentally, -fno-exceptions and -fno-rtti should be added to
> CXXFLAGS, they have size impact as well).

To my knowledge, -fno-rtti changes ABI, and those C++ files are
mostly there to use C++ library (which might use RTTI and exceptions,
to the exceptions thing might not matter).
So I don't believe these options are safe to add.
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