Add note about platform-specific behavior arising from discussion on bug
711019.
diff --git a/Doc/lib/libmath.tex b/Doc/lib/libmath.tex
index 0571b18..5f1d86f 100644
--- a/Doc/lib/libmath.tex
+++ b/Doc/lib/libmath.tex
@@ -17,7 +17,7 @@
number used as a parameter, so that the programmer can determine how
and why it was generated in the first place.
-The following functions provided by this module:
+The following functions are provided by this module:
\begin{funcdesc}{acos}{x}
Return the arc cosine of \var{x}.
@@ -145,6 +145,16 @@
The mathematical constant \emph{e}.
\end{datadesc}
+\begin{notice}
+ Specific exceptions raised in assorted error cases (and even whether some
+ arguments are considered to be exceptional at all) are not defined in any
+ useful cross-platform or cross-release way. For example, whether
+ \code{math.log(0)} returns \code{-Inf} or raises \exception{ValueError} or
+ \exception{OverflowError} is both platform- and release-dependent, and in
+ cases where \code{math.log(0)} raises an \exception{OverflowError},
+ \code{math.log(0L)} often raises a \exception{ValueError}.
+\end{notice}
+
\begin{seealso}
\seemodule{cmath}{Complex number versions of many of these functions.}
\end{seealso}