Compiling for Shared Libraries

Waldek Hebisch hebisch at
Wed Feb 5 23:50:37 CET 2014

Kevan Hashemi wrote:
> I just compiled GPC from sources on both 32-bit and 64-bit Linux 
> machines. On both machines, I'm running Scientific Linux 6.4, a 
> derivative of Red Had Linux 6.4. The local C compiler is 4.4.7 in both 
> cases.
> On the 32-bit machine, I can compile from Pascal to make objects, and 
> link them with libgpc.a to make a shared library. But on the 64-bit 
> machine I find that I must pass -fPIC to GPC to force it to compile 
> position-independent code for the subsequent link. Even then, libgpc.a 
> is position-dependent, so I can't link it into a shared library. So I 
> edit the GPC build's Makefile:
> CFLAGS = -g -O2 -fPIC
> Now I build GPC again and re-install. The new libgpc.a is 
> position-independent, and I can make my shared library.
> Does anyone know why the default on 64-bit is position-dependent, while 
> on 32-bit it is position-independent?

By default gpc builds position-dependent libgpc.  On 32-bit i386
shared libraries may contain position-dependent code, on other
platforms, in particular for amd64 you need position-independent
code in shared libraries.

If you want shared libgpc, after buildiing gpc do:

cd gcc/p/rts
make clean
make WITH_SHARED=yes

I do not remember if there is any support for automatically
installing libgpc, if needed install resulting libgpc by hand.

                              Waldek Hebisch
hebisch at 

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