Fix mmap_is_attached_or_noreserve

[Ken Brown]

On 12/26/2024 11:56 AM, Ken Brown wrote:
> The attached patch attempts to fix the problem reported here:
> 
>    https://cygwin.com/pipermail/cygwin-developers/2024-December/012725.html
> 
> The patch is not ready for prime time because I have been unable to test 
> it.  When I install the patch, mintty hangs on startup without showing 
> the bash prompt, and a grep process is left running.  I can kill the 
> grep process through the Windows Task Manager and then get a bash 
> prompt, but every command I try to run hangs and has to be killed 
> through the Task Manager.  In particular, I can't run the test cases 
> that I sent in the above report.
> 
> So either there's something wrong with the patch or else it triggers a 
> bug somewhere else.  I don't know how to debug this.
> 
> Takashi, do you think this could be related to the signal issues that 
> you've been working on?  The patch potentially eliminates some SIGBUS 
> signals that were raised incorrectly before, and it also potentially 
> causes some (correct) SIGBUS signals that were not raised before.
I tried applying my patch on top of cygwin 3.5.4, and the behavior is 
the same.  So it doesn't seem to be related to the recent signal issues.

Ken