I think it depends. In general, I prefer using expression, but there are cases where using sizeof is better (where better may be clearer, more maintainable, etc

I think it depends. In general, I prefer using expression, but there are cases where using sizeof is better (where better may be clearer, more maintainable, etc...). I think casting malloc is useless in C (not only semantically, but from a readability POV), and is generally correlated with poor C programming. As other mentioned, mozilla is in C++, so that does not apply.