On Tue, Feb 21, 2017 at 12:28 PM, Daniel Krügler <daniel.krueg...@gmail.com> wrote: > Thread-safe initialization of static local function variables is part > of C++11, via > > http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2660.htm > > but > > (a) at least some implementations still do not support them, or > (b) provide means (outside of the spec) that allow to disable this > functionality (gcc: --fno-threadsafe-statics, Visual Studio 2015: > /Zc:threadSafeInit-). > > The compilers I am aware of both don't provide a vendor specific > feature macro to detect this situation. > > I would therefore strongly vote for a feature macro that describes the > presence of that functionality, because user code can usually defend > against this missing feature by means of std::call_once. Here is > therefore a minimalistic example code hopefully suitable for a future > revision of p0096 (The example also shows my current feature macro > name suggestion as "__cpp_threadsafe_static_init"): > > Thingy& get_thing() > { > #ifndef __cpp_threadsafe_static_init > [...] > static std::once_flag flag; > std::call_once(flag, init::get); > return init::get(); > #else > static Thingy result; > return result; > #endif > }
Sounds good to me. Jason _______________________________________________ Features mailing list Features@isocpp.open-std.org http://www.open-std.org/mailman/listinfo/features
