Is it reasonable to null guard every single dereferenced pointer?
- by evadeflow
At a new job, I've been getting flagged in code reviews for code like this:
PowerManager::PowerManager(IMsgSender* msgSender)
: msgSender_(msgSender) { }
void PowerManager::SignalShutdown()
{
msgSender_->sendMsg("shutdown()");
}
I'm told that last method should read:
void PowerManager::SignalShutdown()
{
if (msgSender_) {
msgSender_->sendMsg("shutdown()");
}
}
i.e., I must put a NULL guard around the msgSender_ variable, even though it is a private data member. It's difficult for me to restrain myself from using expletives to describe how I feel about this piece of 'wisdom'. When I ask for an explanation, I get a litany of horror stories about how some junior programmer, some-year, got confused about how a class was supposed to work and accidentally deleted a member he shouldn't have (and set it to NULL afterwards, apparently), and things blew up in the field right after a product release, and we've "learned the hard way, trust us" that it's better to just NULL check everything.
To me, this feels like cargo cult programming, plain and simple. A few well-meaning colleagues are earnestly trying to help me 'get it' and see how this will help me write more robust code, but... I can't help feeling like they're the ones who don't get it.
Is it reasonable for a coding standard to require that every single pointer dereferenced in a function be checked for NULL first—even private data members? (Note: To give some context, we make a consumer electronics device, not an air traffic control system or some other 'failure-equals-people-die' product.)
EDIT: In the above example, the msgSender_ collaborator isn't optional. If it's ever NULL, it indicates a bug. The only reason it is passed into the constructor is so PowerManager can be tested with a mock IMsgSender subclass.
