C++ STL library error: Non-const function ... called for const object

Question

Hello,
I'm using the Forte Developer 6 Update 2 C++ compiler and standard library on Solaris 9 SPARC. I've installed the recommended patch set for C++ (both the workshop and platform patches).
In my code, I have a STL set with some elements that I want to modify, say:
typedef set<SomeClass> MySet;
typedef MySet::iterator MySetIter;
I'm trying to look for an element, then update some of its fields:
MySet theSet;
SomeClass sci;
MySetIter it = theSet.find(sci);
if (it != theSet.end()) {
it->update_some_fields();
The above code fails with the following error (some details scrapped):
Error: Non-const function SomeClass::update_some_fields() called for const object
Which is weird, since set::find() seems to return a set<...>::iterator, not a set<...>::const_iterator!
If I try a workaround, like this:
if (it != theSet.end()) {
SomeClass &tmp = *it;
tmp->update_some_fields();
I get this other error:
Initializing SomeClass& requires an lvalue.
Is there some way to convince the Forte compiler to work around this situation (most likely a compiler / library bug)?

Answer 1

This was fixed, too, by replacing the set with a map. It seems that the issue was related to the fact that any change made to a set member is supposed to not modify the elements that make up the key (the elements that are used in the comparison function to determine the ordering). The Windows (dinkumware) implementation of the STL allows set modifications, though I don't know how they check that the key fields are not modified. The Solaris implementation (and the GNU implementation, too) disallows any modifications made to set members. At least that's what a person more knowledgeable of C++ in our office found out. So I don't think the issue was related to template constructors or any unimplemented features after all.