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

>>25

It's obvious that pretty much anything C++ can do, you can find some equivalent way in C - that is the nature of Turing-complete languages

Type deduction/auto can't be done in C at all. Syntax is independent of Turing completeness.