\input{umtest-preamble}
\usepackage{unicode-math}
\setmathfont{xits-math.otf}
\begin{document}
\[
\overbrace{a+b+c+d}^{e/f/g/h}
\overbracket{a+b+c+d}^{e/f/g/h}
\overparen{a+b+c+d}^{e/f/g/h}
\]
\[
\underbrace{a+b+c+d}_{e/f/g/h}
\underbracket{a+b+c+d}_{e/f/g/h}
\underparen{a+b+c+d}_{e/f/g/h}
\]
\end{document}
