Re: [patch i386]: PR/39356 name collision of __chkstk

[Kai Tietz <ktietz70 at googlemail dot com>]

2009/3/23 Danny Smith <dansmister@gmail.com>:
> On Mon, Mar 23, 2009 at 3:23 PM, Christopher Faylor
> <cgf-use-the-mailinglist-please@gnu.org> wrote:
>> On Sat, Mar 21, 2009 at 07:32:03PM +0100, Kai Tietz wrote:
>>>Not me. AFAIK NightStrike just mentioned that for 4.3 the issue didn't
>>>happened. I assume it is poped up by using shared libgcc, because here
>>>the symbol get in conflict with the exports of kernel32.dll and
>>>ntdll.dll (we provided in our runtime). So the bug was already
>>>present, but it's present just showed up in 4.4.
>>>Just by this reason NightStrike sees this as regression and I can't
>>>say that this is wrong from an user point of view. It seems to me that
>>>this is a bug with a long history.
>>>
>>>For me it is not urgent, but we have to life with that hack in our crt
>>>for the long time of 4.4 and we come to same catch 22 situation I
>>>would like to avoid. so I would like to see it 4.4. And it fixes a
>>>latent bug also for 32-bit win32 targets, present now for a long time.
>>
>> I guess I have no objections to this being included if Danny agrees
>> to withdraw his objection.
>>
>> cgf
>
> I have no strong objections, but I would really like to understand why
> this patch is so urgent.
>
>
> libgcc exports "__chkstk" (prefixed with an additional underscore in assembler)
> ntdll.dll ?exports "_chkstk" (prefixed with an additional underscore
> in assembler).
>
> ntdll.dll is not part of the documented userland win32api. ?To my
> knowledge, it is not included in the Platform SDK.
> I do not know how you created or use the import lib for ntdll.dll
>
> On my Windows XP ?system kernel32.dll exports neither __chkstk nor _chkstk
> by name.

We used to generate for (64-bit) the tool gendef (an earlier and a bit
adjusted version of it). So we simply used the approach export each
symbol from default DLLs. Yes it seem so, that on 64-bit systems the
__chkstk (for older OSes the chkstk.o) is getting exported by
kernel32.dll and ntdll.dll.

> How does the ntdll.dll export of ?"_chkstk" cause you problems in 4.4
> but not in 4.3.
> WTF ?has changed.

The change is the shared libgcc.dll. This symbol is now exported by
it. For 4.3 the static version was used. So the exports from
kernel32/ntdll can collide with libgcc version, when the link order is
changed in that way, that kernel32 is linked before libgcc.

> Danny
>

Cheers,
Kai

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