Thread-safe vector: Is this implementation thread-safe?

Question

I have a question regarding the term thread-safety. Let me give an example:

#include 
#include 

/// A thread-safe vector
class Th         


        

Answer 1

IMHO:

This is both safe and useful:

  void add(double d) {
    std::lock_guard lg(m);
    v.emplace_back(d);
  }

This is safe but useless:

  // return length of vector  
  int length() {
    std::lock_guard lg(m);
    return v.size();
  }   

Because by the time you've got your length it may well have changed, so reasoning about it is unlikely to be useful.

How about this?

template
decltype(auto) do_safely(Func&& f)
{
  std::lock_guard lock(m);
  return f(v);
}

called like this:

myv.do_safely([](auto& vec) { 
  // do something with the vector
  return true;  // or anything you like
});