Among the attributes that can be specified is a thread's stack size. The default attributes structure specifies a stack size that is probably good enough for most applications. How big is it? The default stack size is not mandated by POSIX. In Digital Unix 4.0, the default stack size is 21,120 bytes, while in Solaris it is one megabyte.

How large a stack is necessary? The answer, of course, is that it depends. If the stack size is too small, there is the danger that a thread will attempt to overwrite the end of its stack. There is no problem with specifying too large a stack, except that, on a 32-bit machine, one should be careful about using up too much address space (one thousand threads, each with a megabyte stack, use a fair portion of the address space).