Re: [Mingw-w64-public] alloca()-Problems, a smoking gun & no resolution yet.

[Kai T. <kti...@go...>]

2009/3/15 Shaun Barlow <sha...@gm...>:
> Hi,
>
>> Ok, I found the issue. Your application calls __chkstk from kernel32,
>> which is pretty false. Because the MS variant just probes the stack,
>> but does not allocate it as the cygwin variant. There are two possible
>> ways to solve this, a) Remove the export from kernel32.def in lib64,
>> or rename the method in gcc/config/i386 defined in cygwin.asm and
>> referenced in i386.md
>
> Thank you very much to Wolfgang for making the testcase, and Kai for
> finding the problem :)
> Applying Kai's solution a) Remove the export from kernel32.def in
> lib64, to a local checkout
> of the mingw-w64 crt has gotten rid of the segfaults I was
> experiencing in my program
>
> In my opinion, solution a) would be the correct course because it
> matches the behaviour of both
> the mingw project's export library and Microsoft own export library
> (referencing __chkstk in either
> and then linking to kernel32 gives an unresolved symbol). Its naming
> (double underscore prefix), would
> also seem to indicate that it is not intended for outside use.
>
> It is obviously Kai's decision which route to take.
>
> Thanks and best regards,
> Shaun
>

Yes, this issue is a bit annoying and is ported from mingw32. I
disabled temporary the export symbol __chkstk in ntdll.def,
kernel32.def, and ntoskernl.def. So always the variant of gcc is used
and those kind of errors a prevented. But this means of course that vc
generated libraries, which are using __chkstk will fail (as the do on
32-bits).
I want to provide a change in 4.5 gcc to avoid this issue completely
and allow the co-existance of gcc's and vc's stack checking routine
for 64-bit and 32-bit by renaming the gcc's variant to __gnu_chkstk.

Fix is on mingw-w64 trunk rev.678.

Cheers,
Kai


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