Thread-local storage can be available in betterC

[9il]

Could you please provide more information here. It is very interesting if this is already true

[n8sh]

This forum post by Walter Bright from June 2017:

Does the TLS implementation depend on druntime on any other platforms?

For a C implementation that doesn't support TLS, using it in D with -betterC won't work.

Followed by this post from Walter Bright:

I'm thinking more of a C implementation where it does work. But perhaps you're not expected to do anything besides what you can do in C when it comes to TLS.

It does work with C on Windows, Linux, OSX, and FreeBSD, and so it works with -betterC, too.

---

This little program compiles with dmd -betterC/ldc2 -betterC and exits with 0.

int foo()
{
    static int x;
    return ++x;
}

extern(C) int main(int argc, char** argv)
{
    assert(1 == foo());
    return 2 - foo();
}

[jmh530]

@n8sh What about something like below, but just adding in whatever is known to not have TLS (I have not verified these, just throwing it out there)?

version (D_betterC) {
    version(CRuntime_DigitalMars) {
        version = D_betterC_CRuntime_withoutTLS;
    } else version(CRuntime_Glibc) {
        version = D_betterC_CRuntime_withoutTLS;
    } else version(CRuntime_Microsoft) {
        version = D_betterC_CRuntime_withoutTLS;
    }
}

version (D_betterC_CRuntime_withoutTLS) {
    private enum bool THREAD_LOCAL_STORAGE_AVAILABLE = false;   
} else {
    private enum bool THREAD_LOCAL_STORAGE_AVAILABLE = __traits(compiles, { static size_t x = 0; });
}

[9il]

@n8sh please follow @jmh530 suggestion

[n8sh]

@9il Sounds like a plan. I'll perform investigation of specific compiler / C runtime combinations.