Clarified documentation of tempnam().
Closes SF bug #635656.
diff --git a/Doc/lib/libos.tex b/Doc/lib/libos.tex
index bc935b2..cf68f60 100644
--- a/Doc/lib/libos.tex
+++ b/Doc/lib/libos.tex
@@ -972,6 +972,10 @@
filename. Applications are responsible for properly creating and
managing files created using paths returned by \function{tempnam()};
no automatic cleanup is provided.
+On \UNIX, the environment variable \envvar{TMPDIR} overrides
+\var{dir}, while on Windows the \envvar{TMP} is used. The specific
+behavior of this function depends on the C library implementation;
+some aspects are underspecified in system documentation.
\warning{Use of \function{tempnam()} is vulnerable to symlink attacks;
consider using \function{tmpfile()} instead.}
Availability: \UNIX, Windows.