https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113203
--- Comment #8 from Stefan Krah <stefan at bytereef dot org> --- As Richard wrote, C99 demands that an additional out-of-line copy of the function is generated. Whether the non-standard __attribute__ ((always_inline)) should override C99 is of course another question. For users the strictness of always_inline seems tricky. I'd welcome an additional "really_inline" that ignores the heuristics but does not fail with a compile error if inlining is not possible.
