If library fixedpointarithmetic is loaded and enabled, the functions max
and min are broken:
% plain TeX
\input pgfmath
\input fp
\usepgflibrary{fixedpointarithmetic}
\pgfset{fixed point arithmetic}
\pgfmathmax{2}{100}
\immediate\write16{max(2, 100) = \pgfmathresult}
\csname @@end\endcsname\end
The error message is:
! FP error: Illegal character \immediate found in float number!.
That means, the implementation of \pgfmathmax is reading the next token
after the two arguments.
Thank you for reporting. This should be fixed now.