Question

I have a lot of multithreading bugs since I introduced a second worker thread. The issues are minor and hard to trace. My latest indications point to

class MyOtherClass {
    static String defaultName;
    static String getDefaultName() {return defaultName;}
}

which is being used by:

result plainLocalFunction() {
    result r = E_SUCCESS;
    String fallbackName = MyOtherClass::getDefaultName();
    //Do other stuff with locals.
    return r;
}

I’ve been ages debugging this and I can only suppose that either the plainLocalFunction is shares its locals between threads or that that the call to getDefaultName() involves writing to a static variable which is not thread safe? Thanks for your time.

Answer 1

static variables inside a function would render your function not re-entrant and not thread safe.

If you have just local variables in a function then each thread stack will have its own copy of those variables and the function will be thread safe.