illumos gate

I think it's fine the way it is. It's an operator, not a function; the space reflects that visually.

I agree with Joshua. While it's unfortunate that our style is different than other styles, we have a style guide and a long history behind it. If we wanted to switch to a style supported by one or more of the BSDs to facilitate code exchange, then that is something that should be considered and done as a whole, rather than trying to sneak in minor changes like this that will only serve to make our own code base inconsistent with itself.

It's not only BSDs, and the reason to not require a whitespace (IMO, of course) is that sizeof() is more function-like, returning value, not control operator, like for, while, or return.

And this is the only real style difference that I see as required by others -- yes, BSDs and those linux parts that actually care about style.

Actually, sizeof is operator in a form of sizeof X, where X can be either variable, or type (or typecast, to be exact). For example, the following is valid C code:

size_t s;
int a;

s = sizeof a;
s = sizeof (int);