\documentclass{article}
\usepackage{acro}
\AtEndDocument{\printacronyms}
\DeclareAcronym{gnu}{
short = GNU ,
long = GNU's Not Unix
}
\DeclareAcronym{gpl}{
short = GPL ,
long = \acs{gnu} General Public License
}
\begin{document}
\ac{gpl}.
\end{document}
fails with the error:
! Missing number, treated as zero.
<to be read again>
\l__acro_pages_list_display_bool
l.17 \end{document}
[Issue discussed on TeX.SE.]
The compilation of the following MCE:
fails with the error: