Do I need to protect read access to an STL container in a multithreading environment?

Question

I have one std::list<> container and these threads:

• One writer thread which adds elements indefinitely.

• One reader/writer thread which re

Answer 1

Whether or not size() is safe (for the definition of "safe" that you provide) is implementation-dependent. Even if you are covered on your platform, for your version of your compiler at your optimization level for your version of thread library and C runtime, please do not code this way. It will come back to byte you, and it will be hell to debug. You're setting yourself up for failure.

Answer 2

You should consider some SLT implementation might calculate the size when called.
To overcome this, you could define a new variable

volatile unsigned int ContainerSize = 0;

Update the variable only inside already protected update calls, but you can read / test the variable without protection (taking into account you don't need the exact value).