Sepples with structs

Every time I see that posted I wonder how that'll work in practice. I'm interested to know if there is any real world example of that in from of a useful library. Filesystem, Graphics, Threads, Algorithms, or whatever is there.
And obviously not a C library,

>>8
structs are more efficient, dont have vtables and are backward compatible with C. You can also convert any memory area to struct, without caring about contructors/destructors. In other words, stucts are the blunt tool that does the job done.