Re: To compile a .so lib

[Arun Sharma <adsharma@xxxxxxxxxxxxxxx>]

On Fri, Feb 25, 2000 at 11:39:48PM +0530, Binand Raj S. wrote:
> Arun Sharma forced the electrons to say:
> > On Fri, Feb 25, 2000 at 06:18:26PM +0530, G Gautam wrote:
> > > I have the source for openssl, but when I compile, I get an .a archive.
> > > Lynx wants a .so library. How do I compile, so that I get a .so library ?
> > 
> > gcc -shared *.o  -o libfoo.so
> 
> Shouldn't that be:
> 
> gcc -shared -Wl,-soname,libfoo.so -o libfoo.so *.o
> 
> Arun? Isn't that -W necessary?

If you want to get the ELF major/minor version numbers right. The correct
linker line is:

gcc -shared -Wl,-soname,libfoo.so.M -o libfoo.so.M.m *.o

Where M = major version of libfoo.so and m = minor version. Further you
link apps with libfoo.so using:

gcc *.o -o app -lfoo

When you do that, you can use a new minor version of libfoo.so, without
relinking your app and not break binary compatibility.

The following URL explains the rationale and the nuts and bolts.

http://www.netbsd.org/Documentation/elf.html#rpath

The FreeBSD handbook lists this as a requirement, but doesn't explain
the rationale.

http://www.freebsd.org/handbook/porting.html, section 4.4.6.4.

For more research - look for DT_SONAME in the ELF specification.

	-Arun