FieldCreate::Helper - pure virtual function call

[mdavidsaver]

I've had two reports of a crash in the compare() call below in two different environments (gcc/Linux and msvc/win32).

pvDataCPP/src/factory/FieldCreateFactory.cpp

Lines 60 to 63 in 17fa7a7

	for(; itp.first!=itp.second; ++itp.first) {
	Field* cent(itp.first->second);
	FLD* centx(dynamic_cast<FLD*>(cent));
	if(centx && compare(*centx, *ent)) {

The WIN32 case specifically gives an error "pure virtual function call" which suggests to me that this isn't simply *NULL.

[mdavidsaver]

While I don't understand the crash well, I think my use of dynamic_cast here, on an object which may have started destruction, is suspect. This code is synchronized with ~Field(), and valgrind doesn't report a data race. However, it might be straight undefined behavior.

In any event, use of dynamic_cast is actually an "optimization" here, and can simply be omitted by dd24b2a. We'll see if there are any further occurrences.

[mdavidsaver]

May be fixed as of 95d4528 in Module 8.0.1 Base 7.0.3.1

[mdavidsaver]

Based on user feedback, probably fixed.