C functions frequently produce more information than just the
returned value. Changing values of arguments with pointers or
arrays, changing global data, and I/O make a function unsafe to
parallelize. The no side effects assertion indicates
that all of the functions named can be assumed to be safe to execute
concurrently. This means that they perform no I/O and they modify
only local variables. If pointers or array names are passed to the
routines, it is assumed that the memory locations they represent are
not modified. The functions named by the #pragma _KAP no side
effects () must have been declared before the assertion.
#pragma _KAP
no side effects () assertion tells KAP to assume that all
external functions are thread-reentrant. This will override KAP
default behavior, which is to assume that all external functions
are NOT thread-reentrant or thread-safe. If the external functions
are not thread-safe, and you use #pragma _KAP no side effects
() , your program may not execute correctly. For example,
local variables in functions are thread-safe only if they are stored
as thread-specific data. See the Guide to DECthreads for
further information on thread-safe functions.