It seems that the standard include file math.h has a define for trunc, this gives issues with std::ios::trunc symbol (defined in e.g. ios). The following code snippet does not compile with cgt-6000 8.3.9 and shows how the problem can be replicated.
#include <iostream> // includes ios and thus std::ios::trunc is defined
#include <math.h> // implements trunc with a define to e.g. __c6xabi_trunc, rather than an inline function
#include <fstream> // looking for std::ios::__c6xabi_trunc instead of std::ios::trunc
