bug#74805: 30.0.92; Trying to build scratch/igc on Cygwin

[Richard Brooksby <rb@ravenbrook.com>]

On 2024-12-22 08:24, Richard Brooksby wrote:
> On 2024-12-21 16:56, Ken Brown wrote:
>> On 12/21/2024 2:24 AM, Eli Zaretskii wrote:
>>>> Date: Fri, 20 Dec 2024 18:48:37 -0500
>>>> Cc: 74805@debbugs.gnu.org, Richard Brooksby <rb@ravenbrook.com>
>>>> From: Ken Brown <kbrown@cornell.edu>
>>>> 3. The "mmap" branch is a straightforward port, mostly imitating the
>>>> FreeBSD port.  It currently (with Cygwin 3.5.5) fails because of a
>>>> limitation of Cygwin's mmap.  But I have a simple patch to Cygwin in 
>>>> the
>>>> works that removes that limitation.  With that patch, 37 of the 38 MPS
>>>> tests pass.  I still need to debug the failing test.  I'm cautiously
>>>> optimistic that I can get this approach to work.  Either way, I expect
>>>> the Cygwin patch to soon be available in a test release of Cygwin 3.6.0
>>>> so that other Cygwin users can try it.
>>>
>>> Thanks for the update, I think this is very good news.
>>
>> I could use some help from the MPS experts in debugging the failing 
>> test, which is arenacv.  I ran the test under strace and didn't see 
>> any mmap or munmap failures.  I'm attaching the test log, which 
>> doesn't mean a thing to me.  I also built an unoptimized arenacv and 
>> can run it under gdb if someone tells me what to look for.
> 
> Hello.  I can't offer much direct help just now, but here's where I'd 
> start.
...
 > It's very unlikely that you're actually running out of address space 
on a 64-bit system.

I should add that arenacv is a coverage test that is *trying* to provoke 
the ResRESOURCE error paths in some circumstances 
https://github.com/Ravenbrook/mps/blob/9fd0577cf1231e61c9801c81499e5d16d0743806/code/arenacv.c#L461 
but note that this isn't where the test is failing.  However, it may be 
relevant, perhaps if your munmap doesn't successfully free address space.