The idea that it does nothing is a persistent myth. Both GCC and Clang heed it although neither treats it as a mandate: https://tartanllama.xyz/posts/inline-h

The idea that it does nothing is a persistent myth. Both GCC and Clang heed it although neither treats it as a mandate: https://tartanllama.xyz/posts/inline-hints/ https://tartanllama.xyz/posts/inline-hints/ This library seems to have the annotation on every function, though, so it's possible the author is just following a convention of always using it for functions defined in header files (it'd be required if the functions weren't declared `static`).