[GHC] #11522: maxStkSize can overflow

[GHC]

#11522: maxStkSize can overflow
-------------------------------------+-------------------------------------
           Reporter:  rwbarton       |             Owner:
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Runtime        |           Version:  7.8.4
  System                             |
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 The `maxStkSize` field of `GC_FLAGS` is a `nat`, or `unsigned int`. It's
 measured in words, but still 32G is not an unreasonable amount of memory
 by today's standards.

 Maybe it's unlikely that anyone would want to set the stack size limit to
 more than 32G. But if you happen to have just over 40G of physical memory
 then the default stack size limit will overflow to a value just above zero
 and then Bad Things would happen.

 If we want to actually enforce stack limits that are greater than 2^32^
 words, we would need to increase the size of the `tot_stack_size` field of
 a TSO also.

 Simple test of overflow behavior: `ghci +RTS -K32.0001G` will exit with a
 stack overflow.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11522>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler