Are unused includes harmful in C/C++?

Question

What are the negative consequences of unused includes?

I\'m aware they result in increased binary size (or do they?), anything else?

Answer 1

Whether or not they increase the binary size really depends on what's in them.

The main side-effect is probably the negative impact on compilation speed. Again, how big an impact depends on what's in them, how much and whether they include other headers.