I have an issue with the destruction of a thread_local static object.
#include <iostream>
#include <thread>
struct UsesLoc {
UsesLoc() {
loc.counter++;
}
struct Loc {
Loc() {
std::cout << "I am at " << this << " and counter is " << counter << std::endl;
}
~Loc() {
std::cout << "I was at " << this << " and counter is " << counter << std::endl;
}
int counter = 0;
};
static thread_local Loc loc;
};
thread_local UsesLoc::Loc UsesLoc::loc;
int main()
{
{
UsesLoc usesloc;
std::cout << "loc is at " << &UsesLoc::loc << " and counter is " << UsesLoc::loc.counter << std::endl;
}
return 0;
}
As expected, compiling and running on https://coliru.stacked-crooked.com/a/e8bcfdaffa6a6da7 reveals that the thread_local object is always at the same location and the counter values are (0,1,1):
I am at 0x7f9dc817673c and counter is 0
loc is at 0x7f9dc817673c and counter is 1
I was at 0x7f9dc817673c and counter is 1
Conversely, when I locally compile with MinGW and run, I get, for instance,
I am at 0x507874 and counter is 0
loc is at 0x507874 and counter is 1
I was at 0x7efdd000 and counter is 2686552
Clearly, an uninitialized object at a different memory location is destroyed.
Did I oversee anything non-deterministic? How can I ensure that the correct object is destroyed?
After getting a hint from Ted Lyngmo that this might be a compiler bug, I did a bit of research and it seems to be indeed an issue already reported before:
That being said, the code is correct and the pointer to the object being destructed points to the same object that was constructed before when using a standard-compliant compiler.