Is C++'s new operator reentrant (or async-safe)?

Question

The background is in this question of mine. Put shortly, I have to fork in a multithreaded C++ program, so I\'d like to figure out how much I can do when r

Answer 1

I've looked at both the gcc libsupc++ and clang libc++ source, for replacing the standard-conforming C++ new/delete operators - to support native SIMD alignment requirements on platforms where it wasn't guaranteed by malloc.

They are basically wrappers for malloc and free with some EH logic, etc. I am not a language lawyer, but unless both have it wrong, I think it's safe to conclude: no, they are not reentrant.

Answer 2

Standard allows new to be just a wrapper around malloc, so if malloc can be not reentrant, so can new.

Answer 3

Thread-safety and re-entrance are not exactly the same.

AFAIK, the C++ ISO standard does not guarantee thread-safety for new and delete operators. But g++ implementation does provide thread-safetly (and it's one of the reasons it's slow).