On Monday, 11 September 2017 at 22:38:21 UTC, Walter Bright wrote:
If an address is taken to a TLS object, any relocations and adjustments are made at the time the pointer is generated, not when the pointer is dereferenced.
Could you elaborate on that explanation more? The way I thought about it was that no matter where the data is actually stored (global, static, tls, heap, etc.), in order to access it by pointer it must be mapped into virtual memory (address) space. From that it follows that each thread will have its own "slice" of that address space. Thus, if you pass an address into such a slice (that happens to be mapped to the TLS of a thread) to other threads, you can manipulate the first thread's TLS data (and cause the usual data races without proper synchronization, of course).
