[dmd-internals] __tls_callbacks_a

[Alex]

Problem is that the symbol is a strong reference, so redefining it
will just give a duplicate symbol error. :/

Regards,
Alex

On Thu, Jan 19, 2012 at 10:28 PM, Rainer Schuetze <r.sagitario at gmx.de> wrote:
>
> Can't you declare the symbols (_tls_index and _tls_used) in the tlsdata
> module elsewhere (not in a library), so the module will not be taken from
> the library? Then you can set your own list of callbacks.
>
>
> On 19.01.2012 22:11, Alex wrote:
>>
>> Hi,
>>
>>> Maybe you can patch the corresponding entry off the _tls_used data struct
>>> very early, so the TLS callback are called when necessary.
>>
>> Unfortunately, it seems the PE loader loads it immediately, so
>> patching at runtime is virtually impossible. :(
>>
>> (We did think of doing a horrible hack (detouring
>> LdrShutdownThread()), but this is insane for many reasons...)
>>
>> My guess is that the symbol is just defined always for convenience, as
>> it's necessary for C/C++ code using TLS. However, this clearly imposes
>> problems on D users, as we have no way of utilizing the symbol
>> correctly.
>>
>> The last resort is to simply patch snn.lib but this obviously
>> complicates the build process a LOT. We'd really like to avoid this...
>>
>> Regards,
>> Alex
>>
>> On Thu, Jan 19, 2012 at 9:38 PM, Rainer Schuetze<r.sagitario at gmx.de>
>>  wrote:
>>>
>>> _tls_callbacks_a is defined to a single zero entry in the C runtime
>>> library,
>>> see the module tlsdata.obj from snn.lib.
>>>
>>> I guess you know this, but here's a very in depth article about TLS under
>>> windows: http://www.nynaeve.net/?p=183
>>>
>>> Maybe you can patch the corresponding entry off the _tls_used data struct
>>> very early, so the TLS callback are called when necessary.
>>>
>>>
>>> On 19.01.2012 11:40, Alex wrote:
>>>>
>>>> Anyone have a clue? As said, this is quite essential for implementing
>>>> a TLS-supporting VM in D.
>>>>
>>>> Regards,
>>>> Alex
>>>>
>>>> On Tue, Jan 17, 2012 at 8:59 AM, Alex<xtzgzorex at gmail.com>    wrote:
>>>>>
>>>>> Hi,
>>>>>
>>>>> It seems that either DMD or Optlink is emitting this symbol, most
>>>>> likely because it was expected that users would like to define TLS
>>>>> callbacks. However, in D we have nothing like _CRTALLOC() or
>>>>> __declspec(allocate()), so we cannot specify that we want a callback
>>>>> registered there. This callback is rather essential for a virtual
>>>>> machine that me and a few others are working on, so is there some kind
>>>>> of workaround we could use? Or perhaps we're just missing the way this
>>>>> is supposed to used in the first place?
>>>>>
>>>>> Regards,
>>>>> Alex
>>>>
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