[Bug c/88727] Diagnostics improvement: Detection of undefined behaviour. Incomplete type in tenative definition with internal linkage. [-Wtentative-definition-incomplete-type]

[jsm28 at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88727

--- Comment #5 from Joseph S. Myers <jsm28 at gcc dot gnu.org> ---
Since C2y allows this construct, this is now a quality-of-implementation issue
only for older standard versions and for -Wc23-c2y-compat.