To see a non contrived example where the change breaks existing documents, take this example (using a math expression from the breqn package documentation)
\documentclass[]{article} \usepackage{breqn} \begin{document} aaaaaaaaaaaaaaaaaaa \begin{dmath*} g = 0 + 1 - 1 \end{dmath*} aaaaaaaaaaaaaaa \begin{dmath*} T(n) \hiderel{\leq} T(2^{\lceil\lg n\rceil}) \leq c(3^{\lceil\lg n\rceil} -2^{\lceil\lg n\rceil}) <3c\cdot3^{\lg n} =3c\,n^{\lg3} \end{dmath*}. \end{document} I attach the output from xelatex 2014 and 2015, basically breqn doesn't work with xelatex 2015. I haven't fully traced it but I suspect (since math lists are opaque now) that this is not fixable by changing macro code. David
-------------------------------------------------- Subscriptions, Archive, and List information, etc.: http://tug.org/mailman/listinfo/xetex