What are advantages of using Sepples?

1.templates are easily replaced by macros and _Generic (which selects arguments by compile-time type(without any float/int promotions!)
2.function overload is replaced by above as well.
3.Classes are essentially structs with function pointers.
GCC supports constructors(attribute constructor) and destructors(attribute cleanup) in plain C
http://stackoverflow.com/questions/1113409/attribute-constructor-equivalent-in-vc
http://echorand.me/site/notes/articles/c_cleanup/cleanup_attribute_c.html
4.constexpr can be rewritten as expression macros ({macro;return var;}) which will be optimized via constant propogation(but unlike constexpr can be runtime dependent).
5.GCC has new apply function for plain C
https://gcc.gnu.org/onlinedocs/gcc/Constructing-Calls.html#Constructing-Calls
6.Thread-safe atomics built-ins in Plain C
https://gcc.gnu.org/onlinedocs/gcc/_005f_005fatomic-Builtins.html#g_t_005f_005fatomic-Builtins

>>10

while private properties are defined in the headerfile. Wtf?

Likewise, what the literal fuck.
It brings barely any advantages for being an absolute nuisance.

Who in the right mind thinks "golly gee wiz better shoehorn that geat ol' pImpl idom into every class because it's so fucking convenient eh, Strusdroop sure is a clever guy".