Mikhail Zabaluev authored Jan 06, 2018 and Philip Withnall committed Feb 09, 2018

Note that the g_convert() API works with byte arrays. It's wrong to
default to utf8 there, because iconv can read and produce strings with
interior nul characters which are not allowed in (type utf8).
The documentation was misleading about that in some places, so that got
corrected as well.

Strings in the locale encoding are annotated as dynamic-length byte
arrays because they don't have any guaranteed format and can contain
nul bytes. For UTF-8 strings in g_*_{from,to}_utf8(), GLib assumes
no embedded nul bytes and the (type utf8) annotations on the UTF-8
parameters and return values remain as they were. Likewise for
(type filename).

https://bugzilla.gnome.org/show_bug.cgi?id=756128