This function is missing on some platforms:
mingw.
@item
+This function is declared in @code{<unistd.h>} instead of @code{<stdlib.h>}
+on some platforms:
+MacOS X 10.3.
+@item
On some platforms (HP-UX 10.20, SunOS 4.1.4, Solaris 2.5.1), mkstemp has a silly
limit that it can create no more than 26 files from a given template. On
OSF/1 4.0f, it can create only 32 files per process.