[patch] build shared libraries

[Peter S. Mazinger]

On Mon, 5 Sep 2005, Bernhard Fischer wrote:

> Hi,
> 
> Attached patch adds CONFIG_BUILD_LIBRARIES.

haven't tested it, only looked at the patch:
1. for shared libs the objects should all be built PIC (use -fPIC instead 
of -fpic -commented currently-, -fpic is probably meaningful only on ppc)
2. use -Wl,-z,defs when linking the libs, to assure that everything is 
defined
3. soname is only meaningful if the libs have versioning, like
libb-1.0.1.so, soname could be libb.so.1 (some would use as libname 
libbb.so.1.0.1 and soname libbb.so.1), versioning would help if
external apps are built against these libs and/or if ABI changes.

> 
> If set, lib*.a will be also build as shared libraries:
> ./libbb/libbb.so
> ./libpwdgrp/libpwdgrp.so
> ./archival/libunarchive/libunarchive.so
> ./networking/libiproute/libiproute.so
> ./coreutils/libcoreutils/libcoreutils.so
> 
> If CONFIG_STATIC is set (which is the default), the busybox binary will
> use the static libs as before.
> 
> If CONFIG_STATIC is not set, busybox will link against the shared
> variants of the libraries (1).
> 
> make install installs (currently, i'm not against changing this) both
> dynamic and static variants of the libraries into $PREFIX/lib[64].
> 
> This patch is ment as an RFC. It worked flawlessly in my cursory
> testing so far.
> Comments?
> 
> 
> 
> 1)
> # ldd bin/busybox
> 	libunarchive.so => /lib/libunarchive.so (0x40018000)
> 	libiproute.so => /lib/libiproute.so (0x400e2000)
> 	libpwdgrp.so => /lib/libpwdgrp.so (0x400f0000)
> 	libcoreutils.so => /lib/libcoreutils.so (0x400f3000)
> 	libbb.so => /lib/libbb.so (0x400f5000)
> 	libdl.so.2 => /lib/tls/libdl.so.2 (0x40105000)
> 	libm.so.6 => /lib/tls/libm.so.6 (0x40108000)
> 	libcrypt.so.1 => /lib/tls/libcrypt.so.1 (0x4012b000)
> 	libc.so.6 => /lib/tls/libc.so.6 (0x40158000)
> 	/lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
> # ls -l bin/busybox
> -rwxr-xr-x    1 0      0        739044 Sep  5 09:38 bin/busybox

I would be interested how big the libs are?

> 
> Annotations:
> a) There are two files in libbb which use libcrypt: correct_password.c
> and pw_encrypt.c. Because of this libbb.so itself has to link against
> libcrypt. Is this intended, given that there is libpwdgrp?

as I understand it, busybox used the version provided by *libc, libpwdgrp 
is meant for systems lacking libcrypt

Peter
> 
> 
> b) every single Makefile.in seems to "handcode" the rule to build static
> archives ($(AR) $(ARFLAGS) $@). The patch adds a generic rule to build
> archives. This rule would be used if one specifies just the
> libname.a: myobj1.o myobj2.o
> dependencies without the redundant "$(AR) $(ARFLAGS)..." lines in all
> Makefile.in's. If a Makefile still has a separate Rule for building the
> archives, this specific Rule would be used instead of the generic one
> from Rules.mk.
> I changed the Makefiles for the libs which now are also built dynamically
> and left the other alone for now. I, personally, don't see a good reason
> not to ditch all remaining specific rules for building the archives but
> would suggest to add the generic rule in one place (like this patch
> does) and peruse this rule.
> 
> 
> 
> 

-- 
Peter S. Mazinger <ps dot m at gmx dot net>           ID: 0xA5F059F2
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