alloc-tls provides the alloc_thread_local! macro, a near-drop-in replacement
for the standard library's thread_local! macro that is safe for use in
implementing a global allocator.
Unlike thread_local!, alloc_thread_local! address the following issues
unique to implementing a global allocator:
- On platforms that support the #[thread_local] attribute, registering
destructors for types that implement Drop requires allocation. When a
thread-local is initialized from a call to an allocation function (malloc,
free, etc), this causes reentrancy. alloc_thread_local! can detect this.
- On Mac, it is not safe to access TLS while a dynamic library is being loaded.
When implementing a Mac dynamic library that provides a global allocator,
alloc_thread_local! can detect whether the library has been loaded or not,
and can avoid using TLS if malloc or other similar calls are made from the
loader itself during loading.
Known limitations:
- alloc-tls does not currently support platforms that do not support the
#[thread_local] attribute.