+Minix 3.1.8, mingw, MSVC 9, BeOS.
+@item
+This header file does not define the type @code{pid_t} on some platforms:
+glibc 2.11, MacOS X 10.5.
+@item
+@code{struct sched_param} is not defined on some platforms:
+Haiku.
+@item
+@code{SCHED_FIFO}, @code{SCHED_RR}, @code{SCHED_OTHER} are not defined on
+some platforms:
+Haiku.