How to use __extension__ and __typeof__ in a minified example in C?

I开发者_开发百科 saw there are such tokens in gcc's source code,

but how to use these 2 tokens?

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__extension__:

GCC uses the __extension__ attribute when using the -ansi flag to avoid warnings in headers with GCC extensions. This is mostly used in glibc with function declartions using long long

__typeof__:

MIN and MAX in C is a good example how it's used. Basically it allows you to declare a variable which has the same type as another variable.