I'm guilty of this when writing C. I really have no desire to learn the language properly (it's hard enough to fit C++ in my brain), so I'll just follow the patterns others have set.

Microsoft does stuff like:

    typedef struct _FOO {
        ...
    } FOO, *PFOO;

Yeah ok fine, I'll do that.

When doing this in your own libraries, be sure to document how to generate the struct tag name from the typedef name. (MS don't do this - but they're not consistent about it anyway.) Then when people see a typedef'd struct used somewhere in a header, they'll know how to forward declare it in their own headers.

What's forward declaring mean?