https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100005
--- Comment #13 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
The same like in C.
I.e.
extern inline __attribute__((gnu_inline, always_inline, artificial)) int foo
(int x) { return x; }
// The above is typically from some header
int foo (int x) { return x; }
// The above is the out of line function definition
