[Bug middle-end/68762] link error for inline function decorated with OpenMP declare simd

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68762

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
You need to provide a out-of-line copy of foo for example by adding a

extern double foo (double d);

to foobar.cpp.  At least if this were C, not 100% sure about C++.

OTOH SIMD support may simply fail to provide proper linkage to the clones.