When the engine is compiled with Clang it appears that the return value
is being written to the WRONG address, either due to the vm_ variables being
changed (unexpectedly) elsewhere, or as a result of bad assembly assumptions;
having a stack variable pointing to where to write the return value seems
to do the trick.
This fixes the case where, for a trap_Register()-like call, weird numbers
are being returned when, during the process, an error message is printed
(which in Tremulous results in a QVM call and (nested) system call).
/dev/humancontroller
1ce8ba0cdb