At a new job, I\'ve been getting flagged in code reviews for code like this: Pow

Question

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

Explanation / Answer

It depends on the 'contract':

If PowerManager MUST have a valid IMsgSender, never check for null, let it die sooner.

If on the other hand, it MAY have a IMsgSender, then you need to check every time you use, as simple as that.

Final comment about the story of the junior programmer, the problem is actually the lack of testing procedures.

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