[c++] #define __atribute__

– The __attribute__ directive is used to decorate a code declaration in C, C++ and Objective-C programming languages. This gives the declared code additional attributes that would help the compiler incorporate optimizations or elicit useful warnings to the consumer of that code.

__attribute__((constructor)) is a GCC compiler extension in C++ that allows you to specify a function that should be executed automatically before the main function of your program.