development packages and multilib

[Björn Persson]

I'm trying to learn how to build packages for Fedora. My first question is 
about multilib development packages.

I know that compiled libraries can be installed in both 32-bit and 64-bit 
versions at the same time, but is this required for -devel packages as well? 
That is, is it normal to compile both 32-bit and 64-bit programs on the same 
host, so that one needs both libwhatever-devel.i386 and 
libwhatever-devel.x86_64, or is it permissible for the two versions of 
libwhatever-devel to conflict with each other?

Björn Persson