🚀 go-pugleaf

When I call semctl, which receives a union as one of its arguments, from a 
program compiled with the SunOS cc compiler, my program works.  When I compile
the same program with gcc, the program aborts.

Similarly, when I call lwp_yield, which receives a structure as its argument,
from a program compiled with the SunOS cc compiler, my program works.
When I compile the same program with gcc, the program aborts.

If I modify either program to pass the address of the union or structure
and compile with gcc, the program works.  I did this because I was once told
that the SunOS cc compiler passes structures and unions by address.

Is there a gcc compiler option that will pass unions and structures in 
a manner that is compatible with the SunOS cc compiler?

Can anyone explain the differences in how the SunOS cc compiler and the 
gcc compiler pass unions and structures?  

If there is not a compiler option to make union/structure passing 
compatible, what is the best way to write the code so that it will work 
with either compiler when making calls to system services that receive 
unions or structures?