maxStkSize can overflow

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.

Trac metadata

Trac field	Value
Version	7.8.4
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Runtime System
Test case
Differential revisions
BlockedBy
Related
Blocking
CC	simonmar
Operating system
Architecture