Baslinux mailing list

[sindi keesan <keesan AT sdf.lonestar.org>]

On Wed, 18 Jan 2006, David Moberg wrote:

> sindi keesan wrote:
> > On Wed, 18 Jan 2006, David Moberg wrote:
> >
> > > I've uploaded it. By changing CFLAGS to -Os (in the makefiles) I
> > > was able to reduce the size by about 30k after compression.

Please provide the URL.

> > What is CFLAGS and how does it affect size?
>
> CFLAGS is a special variable that you can change in most
> Makefiles. It controls the header include locations (e.g.
> -I/usr/include/linux) and optimization flags (e.g. -Os -funroll-loops).
>
> gcc accepts several different 'global' optimization flags:
>
> -O0    no optimization
> -O1    minimal optimization
> -O2    even more "     "
> -O3    etc.
> -O4    max (in recent gccs)
>
> -Os     optimize for size
>
> -O + a number optimizes for speed mainly, but -Os optimizes
> maximally for size. AFAIK you want -Os if you try Linux From
> Scratch, as it will save many megs of disk space.

I thought larger code ran faster (or loaded faster).
If -Os optimizes for both size and speed, why use -02 as default?
With ordinary libraries (not uClibc) do faster executables get larger?

> Apparently, -Os also produces faster code than -O3 or even
> -O4 in most circumstances. That's the consensus from a
> recent discussion on the Linux kernel mailing list.
>
> Just edit all of the makefiles and change every instance of
> -O2 or whatever it is to -Os. Sometimes you can also do
> export CFLAGS="-Os" and then configure and make will
> automatically use that setting.
>
> > Will upx files gzip any smaller?
>
> No. That would be like taking a gzip'ed file and running it
> through gzip again. It's already about as small as it can
> get.

The one I downloaded got a bit smaller when I gzipped, even after upxing. 
Maybe 20-30K.  Your optimized version probably won't.

> > > I suggest that you cut out the middleman (I) and download the
> > > uClibc rootfs to compile lynx yourself when the next version
> > > arrives.
> >
> > Will do, since you have demonstrated that it all works - gcc 2.95.3?
>
> uClibc rootfs comes with gcc 3.4, which worked quite well with
> lynx, openssl, dosemu, and many other packages that I have
> compiled with it.

Is gcc 3.4 compiled dynamically against uClibc?

http://www.uclibc.org/downloads says it has source code

Is what I want root_fs_i386.ext2.bz2 21M?

It says you are supposed to compile it.  Did you say they have a compiled 
version too?  INSTALL says to make config and make and make install.
And that I also need to compile binutils and gcc to use with it.

They have in addition to the root-fs files, some tar.bz2 files 
uClibc-0.9.28.tar.bz2 etc., about 1.7MB.  Are these source code and the 
root_fs precompiled image?   I thought source code was generally bigger 
than the compiled program.  I am utterly confused.

They also have linux-libc-headers-2.4.31 files (4MB) and gcc*.tar.bz2 
10MB.   Headers are not a dynamic executable so I should not need to 
compile them but is this executable or source code for gcc?


> To use the rootfs image, you need a partition with several hundred
> MB of disk space to grow into. bunzip2 it, then mount -o loop.
I am thinking about adding a 9GB scsi drive to one computer.
Does this 21MB expand to several 100MB?

> Then do cp -a /mnt /newdirectory, where /mnt is where it is mounted,
> and newdirectory is where you want to keep it permanently. You
> can then umount /mnt and chroot to newdirectory and start building.

If I am in a directory /uClibc does it use uClibc's root_fs libc and 
binutils and gcc instead of the other ones on my computer?  Or do I need 
to set up a different partition without any other glibc on it?


I think you are overestimating my understanding of linux.
The vocabulary at uclibc.org is strange to me - cross-compiling 
toolchains, etc.

> Most programs should work fine, but you might want to set up some
> symlinks such as ln -s /usr/bin/cpp /lib/cpp.
>
> David