Linkage order in Linux

[michael kapelko]

Hello.
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.
Thanks.