I’ve been using static thread_locals and I observed confusing behavior for thread_local destruction at program exit. In my simplified example, an object owns a thread and joins on it when the object is destroyed. This is derived from a thread pool construct.
The object, defined as Wrapper, is held in a static global and I expect it to be destroyed at the end of main. The issue is that the static thread_local destructor from the spawned thread owned by Wrapper is not called and is reported as a leak by leak sanitizer. However, if I destroy the object before the end of main, the static thread_local destructor is indeed called.
My understanding is that thread_local destructors should be invoked before join returns. Why is it that the thread_local destructor is not invoked when the static global object is destroyed and joins on the thread after main ends?
In the output below, there is a message for the construction of the thread_local, but no corresponding message for the destruction of the thread_local.
clang version 3.7.0 (tags/RELEASE_370/final)
Thread model: posix
clang++ -g -o foo foo.cc -fsanitize=leak -std=c++11 -lpthread
Started 140182605002496 from 140182628901568
Constructed thread_local from 140182605002496
Joining 140182605002496 from 140182628901568
foo.cc (1.86 KB)