Re: [boost] Fwd: Thread-Local Storage (TLS) and templates

From: Peter Dimov (pdimov_at_[hidden])
Date: 2003-02-19 08:30:51

David Abrahams wrote:
> "Peter Dimov" <pdimov_at_[hidden]> writes:
>
>> Looks like a no-brainer, &k can't be a compile-time constant if k is
>> thread-local.
>>
>> 1.
>>
>> void f()
>> {
>>     C<&k> ck;
>> }
[...]
>> The type of ck cannot depend on the thread that is executing f.
>
> It doesn't have to.  When used as a template parameter, an address
> could refer to something more like a member function pointer, i.e. an
> offset in the thread's table of globals.

C has been declared as

template<int * p> class C;

An int* is an int*. I don't think that any implementation has
mini-union-pointers to accomodate thread local addresses. The performance
impact would kill pointers.