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List:       busybox
Subject:    Re: [PATCH 05/19] buildsystem: remove the -static-libgcc flag, saves a few Kb
From:       Rich Felker <dalias () aerifal ! cx>
Date:       2012-09-27 17:51:23
Message-ID: 20120927175123.GC254 () brightrain ! aerifal ! cx
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On Thu, Sep 27, 2012 at 10:19:04AM +0200, Florian Fainelli wrote:
> On Tuesday 25 September 2012 18:42:05 Rich Felker wrote:
> > On Tue, Sep 25, 2012 at 02:06:04PM +0200, Florian Fainelli wrote:
> > > From: Felix Fietkau <nbd@openwrt.org>
> > > 
> > > Signed-off-by: Felix Fietkau <nbd@openwrt.org>
> > > ---
> > >  Makefile.flags |    2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > > diff --git a/Makefile.flags b/Makefile.flags
> > > index e77c0e5..f129cef 100644
> > > --- a/Makefile.flags
> > > +++ b/Makefile.flags
> > > @@ -51,7 +51,7 @@ CFLAGS += $(call cc-option,-fno-builtin-strlen -finline-
> limit=0 -fomit-frame-poi
> > >  # -fno-guess-branch-probability: prohibit pseudo-random guessing
> > >  # of branch probabilities (hopefully makes bloatcheck more stable):
> > >  CFLAGS += $(call cc-option,-fno-guess-branch-probability,)
> > > -CFLAGS += $(call cc-option,-funsigned-char -static-libgcc,)
> > > +CFLAGS += $(call cc-option,-funsigned-char,)
> > 
> > On most systems this flag should be a no-op, but when it's not, you
> > definitely want it. Using shared libgcc might save a tiny amount of
> > space in the binary, but it will add 4-8k of memory usage to each
> > instance of busybox at runtime. This is not a reasonable tradeoff.
> 
> Ok, so maybe we should make this available via some configuration knob? For 
> sure, we'd like to save the space involved by using a statically linked libgcc 
> to busybox. What do you think?

No. If you use shared libgcc, you'll need a >100k .so file lying
around, and each instance of busybox will use an extra 4k of
unsharable memory for libgcc_s.so's GOT. If you static link libgcc,
which is what should always be done, you'll only add a few hundred
bytes to the busybox binary for 64-bit division and such (and maybe
nothing at all if you're on a 64-bit arch where libgcc is mostly
useless).

Rich
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