I'm experimenting with coroutines in C++ using cppcoro. But Address Sanitizer seems always unhappy that I'm leaking memory. Why? I've never allocated anything using raw new/delete and have never cause a circular dependency with shared_ptr.
#include <cppcoro/task.hpp>
#include <cppcoro/sync_wait.hpp>
#include <iostream>
class A {
public:
A() { std::cerr << "A ctor\n"; }
~A() { std::cerr << "A dtor\n"; }
};
int main()
{
auto getACoro = []() -> cppcoro::task<std::shared_ptr<A>> {
co_return std::make_shared<A>();
};
auto foo = [getACoro]() -> cppcoro::task<> {
co_await getACoro();
co_return;
};
auto coro = [&foo]() -> cppcoro::task<> {
co_await foo();
};
cppcoro::sync_wait(coro());
}
Compile with: g++ -std=c++20 -focorutines main.cpp -o main -lcppcoro -g -O -fsanitize=address
Then address sanitizer complains with:
=================================================================
==274677==ERROR: LeakSanitizer: detected memory leaks
Indirect leak of 88 byte(s) in 1 object(s) allocated from:
#0 0x7ff558d7af41 in operator new(unsigned long) /build/gcc/src/gcc/libsanitizer/asan/asan_new_delete.cpp:99
#1 0x560128e69267 in operator() /home/marty/Documents/experiments/cpp/main.cpp:47
#2 0x560128e69267 in main::{lambda()#3}::operator()() const [clone .actor] /home/marty/Documents/experiments/cpp/main.cpp:50
Indirect leak of 80 byte(s) in 1 object(s) allocated from:
#0 0x7ff558d7af41 in operator new(unsigned long) /build/gcc/src/gcc/libsanitizer/asan/asan_new_delete.cpp:99
#1 0x560128e6878e in operator() /home/marty/Documents/experiments/cpp/main.cpp:43
#2 0x560128e6878e in main::{lambda()#2}::operator()() const [clone .actor] /home/marty/Documents/experiments/cpp/main.cpp:45
#3 0x560128f7b997 (/home/marty/Documents/experiments/cpp/main+0x145997)
Indirect leak of 24 byte(s) in 1 object(s) allocated from:
#0 0x7ff558d7af41 in operator new(unsigned long) /build/gcc/src/gcc/libsanitizer/asan/asan_new_delete.cpp:99
#1 0x560128e71168 in __gnu_cxx::new_allocator<std::_Sp_counted_ptr_inplace<A, std::allocator<A>, (__gnu_cxx::_Lock_policy)2> >::allocate(unsigned long, void const*) /usr/include/c++/10.2.0/ext/new_allocator.h:115
#2 0x560128e71168 in std::allocator<std::_Sp_counted_ptr_inplace<A, std::allocator<A>, (__gnu_cxx::_Lock_policy)2> >::allocate(unsigned long) /usr/include/c++/10.2.0/bits/allocator.h:173
#3 0x560128e71168 in std::allocator_traits<std::allocator<std::_Sp_counted_ptr_inplace<A, std::allocator<A>, (__gnu_cxx::_Lock_policy)2> > >::allocate(std::allocator<std::_Sp_counted_ptr_inplace<A, std::allocator<A>, (__gnu_cxx::_Lock_policy)2> >&, unsigned long) /usr/include/c++/10.2.0/bits/alloc_traits.h:460
#4 0x560128e71168 in std::__allocated_ptr<std::allocator<std::_Sp_counted_ptr_inplace<A, std::allocator<A>, (__gnu_cxx::_Lock_policy)2> > > std::__allocate_guarded<std::allocator<std::_Sp_counted_ptr_inplace<A, std::allocator<A>, (__gnu_cxx::_Lock_policy)2> > >(std::allocator<std::_Sp_counted_ptr_inplace<A, std::allocator<A>, (__gnu_cxx::_Lock_policy)2> >&) /usr/include/c++/10.2.0/bits/allocated_ptr.h:97
#5 0xbe0b47d5ffffffff (<unknown module>)
SUMMARY: AddressSanitizer: 192 byte(s) leaked in 3 allocation(s).
As far I can tell. The shared_ptr should have destructed right after co_await getACoro();. Why is it considered leaked? And why are the coroutine frames leaking?
Compiler: GCC 10.2 OS: Linux