When creating c++ threads (with c++ std::thread), the resulting binary has memory leaks when running with qemu-ppc.
Eg the following c++ program, when compiled with gcc, consumes more and more memory while running at qemu-ppc. (does not have memory leaks when compiling for Intel, when running same binary on real powerpc CPU hardware also no memory leaks).
(Note I used function getCurrentRSS to show available memory, see https://stackoverflow.com/questions/669438/how-to-get-memory-usage-at-runtime-using-c; calls commented out here)
Compiler: powerpc-linux-gnu-g++ (Debian 8.3.0-2) 8.3.0 (but same problem with older g++ compilers even 4.9)
Os: Debian 10.0 ( Buster) (but same problem seen on Debian 9/stetch)
qemu: qemu-ppc version 3.1.50
---
#include <iostream>
#include <thread>
#include <chrono>
using namespace std::chrono_literals;
// Create/run and join a 100 threads.
void Fun100()
{
// auto b4 = getCurrentRSS();
// std::cout << getCurrentRSS() << std::endl;
for(int n = 0; n < 100; n++)
{
std::thread t([]
{
std::this_thread::sleep_for( 10ms );
});
// std::cout << n << ' ' << getCurrentRSS() << std::endl;
t.join();
}
std::this_thread::sleep_for( 500ms ); // to give OS some time to wipe memory...
// auto after = getCurrentRSS();
std::cout << b4 << ' ' << after << std::endl;
}
int main(int, char **)
{
Fun100();
Fun100(); // memory used keeps increasing
}
Forgive my ignorance of the C++ threading semantics but when do these threads end? Inspection shows we do clear-up CPU and thread structures on exit. That said we do have a comment in linux-user that says:
/* TODO: Free new CPU state if thread creation failed. */
So I wonder if thread creation is actually failing and and that is where we start leaking?