> Even getenv_r() can't really save you, since another thread may be calling setenv() while the (old) value of an env var is being copied into the provided buff

> Even getenv_r() can't really save you, since another thread may be calling setenv() while the (old) value of an env var is being copied into the provided buffer. Won't that depends on the libc implementation. For example, maybe setenv writes to another buffer, then swaps pointers atomically; wouldn't that work?