On 11/10/2014 05:49 PM, Jonathan Wakely wrote: > On 10 November 2014 16:46, Andrew Haley wrote: >> What do you believe a __builtin does but a standard atomic does not do? > > Both C11 and C++11 only support atomic operations on their "atomic > types" and there's no atomic float type (although I'm not sure the > builtins should really support floating point types either). > > The atomic types are also incompatible between C11, as in C they use > the _Atomic qualifier and in C++ they are struct types. So although > you can write this in both languages, it doesn't have the same > meaning: > > atomic_int i; > atomic_store(&i, 1); > > (Because WG14 made a last-minute change to the design that very > deliberately allowed compatibility between the languages.) Hmm. That is reasonable enough, but given that GCC nonstandardly allows atomic_store() et al to work on float, why prefer a GCC nonstandard builtin? Andrew.
