Linkage order in Linux

[Ian Lance Taylor]

michael kapelko <kornerr@gmail.com> writes:

> Recently I found out a surprising requirement to compile own
> application with Horde3D library (http://horde3d.org/), OpenGL 3D
> graphics engine.
> Horde3D library links to shared GL library. But -lHorde3D must be
> listed *before* -lGL for any application to work correctly. If I link
> the application first to GL, and only then to Horde3D, then it merely
> segfaults when Horde3D's init calls glCreateShader, a GL library
> function.
> We have several speculations about what causes this particular order
> for the linker: http://horde3d.org/forums/viewtopic.php?f=2&t=384
> But I'd like to know real reason of this surprising order of linkage
> requirement.

The mailing list gcc@gcc.gnu.org is for gcc developers.  Questions
about using gcc should be taken to gcc-help@gcc.gnu.org.  Please take
any followups to gcc-help.  Thanks.

Unix linkers are always order dependent, by design.  If -lHorde3D
requires symbols from -lGL, but links successfully even if -lHorde3D
is used after -lGL, then perhaps the references in -lHorde3D are weak
for some reason.  Or there are a few other possibilities; I'm not
familiar with the libraries in question.

One thing is for sure: this has nothing to do with gcc.  gcc does not
include a linker.  If you are using GNU/Linux, then your linker is
almost certainly coming from the GNU binutils, which is a different
project; see http://sourceware.org/binutils/ .

Ian