Is conf.IncludePaths.Add thread safe?

[ghost]

Hey,

I'm trying to debug a tricky behavior where I've noticed sometimes an include path is present and sometimes it is not.

I can't easily share the repro case as this is a private (corporate) fork with some modifications - but it would really help my sanity to know from someone more familiar with C#, sharpmake and the OrderableStrings type if it is safe to Configuration.IncludePaths.Add from different project configure functions?

Thanks

[jspelletier]

Hi,
We got hundreds of those calls in our configure methods for our major engine. So, yes this is possible!

[ghost]

I made a little demonstration that shows the underlying hashset silently fails to add when threads are racing to add to it.

namespace HashSetTests
{
    internal class Program
    {
        static HashSet<int> hs;

        static void Main(string[] args)
        {
            const int range = 10000;
            hs = new HashSet<int>(capacity: range);
            for(int i = 0; i < 100; ++i)
            {
                Parallel.For(0, range, (j, state) => {
                    if (!hs.Add(j))
                    {
                        throw new Exception("hashset add is expected to return true for this obviously unique value");
                    }
                });

                if(hs.Count != range)
                {
                    throw new Exception($"hashset should contain exactly {range} elements currently.");
                }
                Console.WriteLine("Passed iteration");
                hs.Clear();
            }
        }
    }
}

Is it safe to do because IncludePaths and the other OrderableStrings containers are distinct objects when configuring and get merged later or something like that?

Just trying to understand what part of the architecture makes this safe.

[jspelletier]

Hi,
I think I misunderstood your initial question!
Each project is processed in a separate thread and each project is only allowed to modify its own fields. For example, to modify IncludePaths property of a specific configuration, this is done via Configure methods. If you follow the rules, the app is 100% safe.

so if you got ProjectA and ProjectB, you are not allowed to modify the include paths of ProjectB from ProjectA and vice-versa.

There is also some constraint on when those collections can be modified. Also, once the configure methods are all executed, many collections become readonly(there is some checks for that).