[Bug target/79671] [7 Regression] mapnik miscompilation on armv7hl since r235622

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79671

--- Comment #72 from Jason Merrill <jason at gcc dot gnu.org> ---
(In reply to rguenther@suse.de from comment #69)
> As I noted elsewhere union members in C++ seem to be pure convenience and a
> union contains implicit members of all types (well, somehow factor in
> alignment).  Of course Jason argues char[] is special and introduces this
> but I can't find text anywhere to support that or require char[] and not,
> say int[].

This is clarified somewhat in C++17, by

http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0137r1.html

Note that this wording makes only unsigned char[] special, not signed or plain
char[].