What does __inline__ mean ?

Question

I am trying to learn C. Reading through some code, I came across a line like this:

__inline__ void () ...

What does the __inline__

Answer 1

Wikipedia / Inline Function

In computer science, an inline function is a programming language construct used to tell a compiler it should perform in-line expansion on a particular function. In other words, the compiler will insert the complete body of the function in every place in the code where that function is used.

GCC Manual § 5.36

If you are writing a header file to be included in ISO C89 programs, write __inline__ instead of inline. See Alternate Keywords.