That you do not call it recursively by checking that the thread local is nil before invocation.
> a re-entrant general solution is desirable.
I know what you mean, but I just don't know why you want to emulate that in C. There is a real problem of people writing APIs that don't let you pass in data with your function pointer - the thread local method can solve 99% of those without changes to the original API.
But if you really want to do all kinds of first class functions with data, do you want to use C?
That you do not call it recursively by checking that the thread local is nil before invocation.
> a re-entrant general solution is desirable.
I know what you mean, but I just don't know why you want to emulate that in C. There is a real problem of people writing APIs that don't let you pass in data with your function pointer - the thread local method can solve 99% of those without changes to the original API.
But if you really want to do all kinds of first class functions with data, do you want to use C?