Re: Segfault while building on 64-bit Cygwin

[Charles Stanhope]

On 2/6/20, Charles Stanhope <address@hidden> wrote:
> On 2/6/20, Andy Wingo <address@hidden> wrote:
>
>> Given that John said that compilation went fine with
>> GUILE_JIT_THRESHOLD=-1, I think perhaps this problem may have been fixed
>> in the past.  My suspicions are that this issue is an ABI issue with
>> lightening that could perhaps be reproduced by:
>>
>>   git co https://gitlab.com/wingo/lightening
>>   cd lightening
>>   make -C tests test-native
>>
>> Of course any additional confirmation is useful and welcome!
>
> I haven't been able to get guile to compile under Cygwin (just a
> compilation error I haven't had time to track down), but I was able to
> quickly try the above. I get:
>
> Testing: test-native-call_10
> call_10.c:9: assertion failed: e == 4
> /bin/sh: line 1:  7063 Aborted                 (core dumped) ./$test
> make: *** [Makefile:31: test-native] Error 134
>

Andy, I don't know if you'd want to continue this here or on
lightening's gitlab page, but I looked into this a little bit a few
minutes here and there this past weeek. The x86 "fast-call" calling
convention used on Windows x64[0] and shared by Cygwin[1] requires
that the caller reserve 32 bytes of memory on the stack for the callee
to spill the register parameters (even if the callee takes fewer than
four parameters). I think lightening is currently missing that for the
x64 case for Cygwin.

To test the idea, I made a small modification (patch attached) that is
*not* intended as a solution as it doesn't work for the general case,
but it does allow the tests to pass on Cygwin 64.

[0] 
https://docs.microsoft.com/en-us/cpp/build/x64-calling-convention?view=vs-2019
[1] https://cygwin.com/cygwin-ug-net/programming.html#gcc-64

--
Charles

x86-fastcall-stack-reservation.patch
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