Re: [Boost-users] [multi index container] Thread safety

Gottlob Frege wrote:

On 10/5/06, Joaquín Mª López Muñoz wrote:

...

No, it is not safe to insert from two threads into the same container. The thread safety guarantees aplying to Boost.MultiIndex (and to most STL implementations as well) are:

1. Concurrent access to different containers is safe. 2. Concurrent read-only access to the same container is safe

I know the standard says nothing about thread-safety (and I also know they are thinking about saying a few things next time), but I was just wondering what everyone thinks about #2 above - concurrent reads to the same container. I've assumed that in the past as well, but how safe do people think that is? If they add threading to the next standard, will they likely add #2 as a requirement on the standard containers?

It's very likely that #1+#2 will become the default level of thread safety for everything in C++. Of course one would be able to override this default by explicitly specifying in the documentation that a 'const' member function isn't really 'const' from thread safety point of view. But most, if not all, of the standard library will be #1+#2 (just like it offers basic exception safety by default, without it being explicitly documented on a function by function basis).