Handle users requesting a too-small stack size

[Aatch]

pthreads has a minimum stack size of 16KB, if you try to set it to lower than this, pthread_attr_setstacksize will return EINVAL. We don't really handle the errors properly (other than checking the return code), so a user requesting a small stack hits the assert, which isn't very helpful.

There are two options for dealing with this: silently clamp the value to the minimum size for whatever platform we're on, or throw a real error somewhere higher in the callstack with a better error message.

I would just fix it, but I feel I need some input on which choice to make.

[alexcrichton]

I would expect the best way to handle this would be to silently clamp to a minimum stack size. Throwing an error would start exposing platform-specific functionality as your 4k stacks would work on X but when running on Y everything would start dying.

[ghost]

I prefer better error message - when I set stack size explicitly I don't expect it to get clamped, also if I want to write platform-agnostic code I shouldn't be setting stack size explicitly - as imo it's already platform specific.

[liigo]

2014/1/21 Alex Crichton notifications@github.com

I would expect the best way to handle this would be to silently clamp to a
minimum stack size. Throwing an error would start exposing
platform-specific functionality as your 4k stacks would work on X but when
running on Y everything would start dying.

+1, for not exposing platform-specific implementation.