Thread specific memory with language features.

Question

Are there languages that support process common memory in one address space and thread specific memory in another address space using language features rather than through a mechanism like function calls?

process int x;
thread int y;

Answer 1

The Visual C++ compiler allows the latter through the nonstandard __declspec(thread) extension - however, it is severly limited, since it isn't supported in dynamically loaded DLLs.

The first is mostly supported through an extern declaration - unless dynamically linked libraries come into play (which is probably the scenario you are looking for).

I am not aware of any environment that makes this as simple as you describe.

Answer 2

ThreadStatic attribute in C#

Answer 3

C++0x adds the "thread_local" storage specifier, so in namespace (or global) scope your example would be

int x;              // normal process-wide global variable
thread_local int y; // per-thread global variable

You can also use thread_local with static when declaring class members or local variables in a function:

class Foo {
    static thread_local int x;
};

void f() {
    static thread_local int x;
}

Unfortunately, this doesn't appear to be one of the C++0x features supported by Visual Studio 2010 or planned GCC releases.