In gtk-doc.xsl: For acronym (nullable) no value found!
When building gtk-doc for Evolution, there are shown these two warnings on the stderr:
In gtk-doc.xsl: For acronym (nullable) no value found!
In gtk-doc.xsl: For acronym (transfer none) no value found!
which I do not understand. They are for this comment and gtk-doc part: https://gitlab.gnome.org/GNOME/evolution/blob/master/src/em-format/e-mail-part-utils.c#L702
When I change the order in the comment the warning order also changes. There is used the same construct (only in opposite order) in the code too (in e-util), which doesn't produce this warnings. I do not see any real different in building this and the e-util gtk-doc, thus I'm really lost what gtk-doc wants from me.
I see the same warning in the latest Fedora rawhide build log https://kojipkgs.fedoraproject.org//packages/evolution/3.31.1/2.fc30/data/logs/x86_64/build.log which uses gtk-doc.x86_64 1.29-1.fc30.
Looking into the result html files I see there:
<p><span class="annotation">[<a href="http://foldoc.org/nullable">
<span class="acronym">nullable</span></a>][<a href="http://foldoc.org/transfer%20none">
<span class="acronym">transfer none</span></a>]</span></p>
A similar code for e_config_lookup_get_source() shows:
<p><span class="annotation">[<acronym title="Don't free data after the code is done.">
<span class="acronym">transfer none</span></acronym>]
[<acronym title="NULL may be passed as the value in, out, in-out; or as a return value.">
<span class="acronym">nullable</span></acronym>]</span></p>
The build scripts are quite the same, as far as I can tell:
https://gitlab.gnome.org/GNOME/evolution/tree/master/docs/reference/evolution-util
https://gitlab.gnome.org/GNOME/evolution/tree/master/docs/reference/evolution-mail-formatter
Could you help me to understand the warning(s) and help me what to do to avoid them, please?