我总是在想，如果只是（P！=
  NULL）{..}将做的工作。

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它将。

I always think simply if(p != NULL){..} will do the job. But after reading this Stack Overflow question, it seems not.

So what's the canonical way to check for NULL pointers after absorbing all discussion in that question which says NULL pointers can have non-zero value?

I always think simply if(p != NULL){..} will do the job.

It will.