std::call_once without TLS

[Paolo Carlini]

Hi,
> 2009/4/30 Chris Fairles:
>   
>>> Here's an ABI-compatible patch to fix libstdc++/39909, it would be
>>> good if Chris or Benjamin could review it.
>>>
>>> Code using the new ABI will use a lock object on the caller's stack
>>> and provide a pointer to it, if the pointer is NULL then the caller is
>>> using the old ABI the global lock object.
>>>       
>> Many apologize for being absent on this issue.
>>
>> This non-ABI breaking patch applies only to 4.4 right?
>>     
> I don't know. Paolo?
>   
It would apply to mainline and 4_4-branch.
> Preserving the ABI will be needed if users want to link objects
> compiled using call_once from 4.4.0 and 4.5.0 -- but IMHO trying to
> preserve ABI for the experimental C++0x stuff is too difficult and if
> someone uses those features they should be prepared to accept that
> they can't expect compatibility between major releases.
>   
Really, we don't want to add / remove symbols from a version already
delivered to the users. I agree we can tolerate more in case of C++0x
but first we don't have a clean way to do without breaking abi-check and
delivering incomprehensible error messages to the users, second, as I
said already, we don't want to edit in the linker script versions
already delivered to the users (in this specific case 3.4.11 in 4.4.0)

Paolo.

Paolo.