+support setting it explicitly, eg. Unices without pthread_attr_setstacksize).
+If you do not specify the stack size, the system's default value is used.
+
+{\bf Warning:} It is a good idea to explicitly specify a value as systems'
+default values vary from just a couple of kByte on some systems (BSD and
+OS/2 systems) to one or several MByte (Windows, Solaris, Linux). So, if you
+have a thread that requires more than just a few kBytes of memory, you will
+have mysterious problems on some platforms but not on the common ones. OTOH
+just indicating a large stack size by default will give you performance
+issues on those systems with small default stack since those typically use
+fully committed memory for the stack.
+If, on the other hand you use lots of threads (say several hundred, which
+often indicates a design flaw), virtual adress space can get tight unless
+you explicitly specify a smaller amount of thread stack space for each
+thread.
+