alt Hacker NewsUnfortunately, for C++, thats not true. At least with glibc and libstdc++, if you do not link with pthreads, then shared pointers are not thread-safe. At runtime it will do a symbol lookup for a pthreads symbol, and based off the result, the shared pointer code will either take the atomic or non-atomic path.
I'd much rather it didnt try to be zero-cost and it always used atomics...
Replies
woodruffw • yesterday at 5:08 PM
This is, impressively, significantly worse than I realized!
eddd-ddde • yesterday at 7:11 PM
Why use atomics if you don't need them? There really should just be two different shared pointer types.
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True, but that's a fault of the implementation, which assumes POSIX is the only thing in town & makes questionable optimization choices, rather that of the language itself
(for reference, the person above is referring to what's described here: https://snf.github.io/2019/02/13/shared-ptr-optimization/)