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Subject:	Re: Help debugging a dll issue
References:	<b21c0ab1-341b-d6f5-915b-f73973b8079b AT cs DOT umass DOT edu> <CABHT960Yx_bg-NaHWcxePEV+Xz74NaVtsu+NjkrSZs4-62rCOA AT mail DOT gmail DOT com> <3a4d2501-8845-99b6-d58b-544bff5e223f AT cs DOT umass DOT edu> <20160520112618 DOT GC12938 AT dimstar DOT local DOT net> <dcfd0854-b7d0-9598-215c-a5f380b23968 AT cs DOT umass DOT edu> <20160520133659 DOT GD12938 AT dimstar DOT local DOT net>
To:	cygwin AT cygwin DOT com
From:	Eliot Moss <moss AT cs DOT umass DOT edu>
Message-ID:	<739fe087-4386-3916-84e7-368ac27a5ae0@cs.umass.edu>
Date:	Fri, 20 May 2016 09:46:30 -0400
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On 5/20/2016 9:36 AM, Duncan Roe wrote:
> On Fri, May 20, 2016 at 08:02:20AM -0400, Eliot Moss wrote:
>> On 5/20/2016 7:26 AM, Duncan Roe wrote:
>>
>>> Hi Eliot,
>>>
>>> Do you know what is the name of the totally different symbol? (maybe from nm -D)
>>
>> Yes -- I have been using nm and objdump to examine the relevant files.  The dll
>> is called libpypy-c.dll.  The symbol I want to bind to is pypy_main_startup, and
>> its proper value (as returned by nm and objdump) is 0x6410ac60.  The result I
>> get is the value of symbol pypy_g_PyNumber_Negative (an automatically generated
>> C function), which is 0x63443f00.
>>
>> I wonder if these collide in some internal hash table and the hash lookup (or
>> the table building) is broken in some subtle way.
>>
>> Regards -- Eliot
>>
> Does findit give the same answer for both symbols?
>
> If you could build your library and libdl.a with debug (-g) then you might be
> able to see how the lookup goes wrong.
>
> HTH ... Duncan.

Well, the wrong answer comes back from the Windows routine GetProcAddress.  The
bug seems to lie either in the Windows run-time code or in how the dll is being
built.  I am trying giving one of the functions a different name to see what
happens (if it's a hash collision effect, presumably something will show up
different).

Regards -- EM

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