Re: exclusive static or shared

[Ralf Wildenhues]

Hi Christopher,

* Christopher Hulbert wrote on Fri, Feb 17, 2006 at 08:21:07PM CET:
> I normally do not create shared libraries.  The ONE place I do though
> is with Matlab MEX functions which are nothing more than a shared
> library with the mexFunction as an exported function.  I link my
> Matlab code against static libraries that contain my real functions
> (The matlab interface serves exactly that an interface from matlab to
> my C/fortran backend). 

So do you compile your static library code with -fPIC?  Because if not,
then..

> Although it's not advised it works on 3 main
> platforms that we use matlab on x86,x86_64,and win32.

 .. it will fail on x86_64 (for nontrivial code):

echo 'int x = 0; int a() { return x; }' > a.c
gcc -c a.c
ar cru liba.a a.o
echo 'extern int a(); int b() { return a(); }' > b.c
gcc -fPIC -c b.c
gcc -shared -o libb.so b.o -L. -la
| /usr/bin/ld: ./liba.a(a.o): relocation R_X86_64_PC32 against `x' can not be 
used when making a shared object; recompile with -fPIC
| /usr/bin/ld: final link failed: Bad value

If you _do_ build the static library with -fPIC: just consider using a
libtool convenience archive instead of a library.  See the docs for the
differences.

Cheers,
Ralf