Advice requested for fixing issue 17914

[Nemanja Boric]

On Wednesday, 25 October 2017 at 13:26:26 UTC, Steven 
Schveighoffer wrote:
> On 10/23/17 12:56 PM, Brian Schott wrote:
>> Context: https://issues.dlang.org/show_bug.cgi?id=17914
>> 
>> I need to get this issue resolved as soon as possible so that 
>> the fix makes it into the next compiler release. Because it 
>> involves cleanup code in a class destructor a design change 
>> may be necessary. Who should I contact to determine the best 
>> way to fix this bug?
>
> It appears that the limitation applies to mmap calls as well, 
> and mmap call to allocate the stack has been in Fiber since as 
> far as I can tell the beginning. How has this not shown up 
> before?

Although after the stack overflow protection for fibers number of 
mmap calls is the same, _I think_ mprotect actually splits the 
single mmapped region into two (as they share different 
protection bits). This effectively doubles the number of the 
regions. As a workaround (if you have lots of fibers and doesn't 
care about stack overflow protection) you can just pass zero for 
the guardPageSize: 
https://github.com/dlang/druntime/blob/master/src/core/thread.d#L4037