Re: compile glibc without most features

[Sascha Ziemann <szi at aibon dot ping dot de>]

Geoff Keating <geoffk@cygnus.com> writes:

| > is it possible to compile the GNU libc without most features, which
| > are nice for a workstation but unimportant for an embedded system?

Sorry I misused the notation "embedded system" for a small system.
What I really want to create is a boot disk for Linux.

| It sounds like what you really want is newlib, which is designed for
| such embedded systems.  Look at http://sourceware.cygnus.com.

I have problems to link against newlib.  I am not sure, if I
understand the problem right, but newlib-1.8.2 has no crt*.o file and
when I try to link with -nostartfiles, I get the following error:

gcc -L. -static -nostartfiles  hello.o -lc -lnosys  -o hello
/usr/local/i686-pc-linux-gnu/bin/ld: warning: cannot find entry symbol _start; defaulting to 08048080

And when I try to link without -nostartfiles, ld tries to use my
system files and that does not work either:

gcc -L. -static  hello.o -lc -lnosys  -o hello
/usr/lib/crt1.o: In function `_start':
/usr/lib/crt1.o(.text+0xe): undefined reference to `__libc_init_first'
/usr/lib/crt1.o(.text+0x18): undefined reference to `_environ'
./libc.a(exit.o): In function `exit':
/home/olivia/szi/software/smbproxy/1.1.1/bootdisk/newlib-1.8.2/newlib.build/libc/stdlib/../../../newlib/libc/stdlib/exit.c:70: undefined reference to `_exit'
collect2: ld returned 1 exit status
make: *** [hello] Error 1

And by the way: I think it is un economically to maintain a second
clib only to get a precisely defined set of function from the glibc.

So I think glibc is the only lib, that can be used for a Linux boot
disk.  But the single so file is bigger than 2 MB.  Each static link
produces binaries which are about 200 - 400 KB.  In order to select
during boot between CD and NFS the floppy must contain drivers for
NICs, NFS, IDE, ISO9660, EXT2.  I have put them into the kernel, to
remove insmod, but with all the drivers the bzImage is 600k and with
this 5 programs the boot disk is completely full:

1216950  161 -rwxr-xr-x   1 szi      ego        164724 Apr 25 12:55 ./rc
1216904  392 -rwxr-xr-x   1 szi      ego        401292 Apr 25 17:46 ./busybox
1216946  282 -rwxr-xr-x   1 szi      ego        288140 Apr 27 09:35 ./mount
1216951  252 -rwxr-xr-x   1 szi      ego        257132 Apr 27 09:35 ./umount
1216955  251 -rwxr-xr-x   1 szi      ego        256212 Apr 25 14:43 ./ip

The extra mount tool is necessary, because the nfsmount in bussybox
does not work with the 2.3.99-pre5 kernel.

So you see: It is a *pain* to get glibc on a floppy.

I think glibc would be more flexible, when it's configure has some
kind of compatibility option.  I would help much, when one can say
configure --features=unix98 or --features=posix or
--features=my-own-set-of-features

Sascha