seg fault with clang in get_topic() when publishing a message

[zontafil]

I'm trying something like this:

            std::string topic_test = "/test";
            std::string payload    = "test";
            std::stringstream sbuf2(payload);
            const mqtt::message_ptr msg = mqtt::make_message(topic_test, sbuf2.str());

            msg->set_qos(static_cast<int>(qos));

            // Publish the message
            mqtt_client_->publish(msg);

and I get a segfault

==931545==ERROR: AddressSanitizer: SEGV on unknown address 0x03e9000e36d9 (pc 0x7c57ac3bed2f bp 0x7c57a6dff940 sp 0x7c57a6dff940 T2)

5: ==931545==The signal is caused by a WRITE memory access.

5:     #0 0x7c57ac3bed2f in std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::_Alloc_hider::_Alloc_hider(char*, std::allocator<char>&&) /usr/lib/gcc/x86_64-linux-gnu/13/../../../../include/c++/13/bits/basic_string.h:193
5:     #1 0x7c57ac3bed2f in std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::basic_string() /usr/lib/gcc/x86_64-linux-gnu/13/../../../../include/c++/13/bits/basic_string.h:524
5:     #2 0x7c57ac3bed2f in mqtt::message::get_topic[abi:cxx11]() const /tmp/fsw-cmake/deps/Linux-x86_64-6.11.0-1012-oem-Ninja-Clang-19.1.7-lld/paho_mqtt_cpp-v1.5.0/paho_mqtt_cpp-src/include/mqtt/message.h:265
5:     #3 0x7c57ac3c196d in mqtt::delivery_token::delivery_token(mqtt::iasync_client&, std::shared_ptr<mqtt::message const>) /tmp/fsw-cmake/deps/Linux-x86_64-6.11.0-1012-oem-Ninja-Clang-19.1.7-lld/paho_mqtt_cpp-v1.5.0/paho_mqtt_cpp-src/include/mqtt/delivery_token.h:75
5:     #4 0x7c57ac3c196d in void std::_Construct<mqtt::delivery_token, mqtt::iasync_client&, std::shared_ptr<mqtt::message const>&>(mqtt::delivery_token*, mqtt::iasync_client&, std::shared_ptr<mqtt::message const>&) /usr/lib/gcc/x86_64-linux-gnu/13/../../../../include/c++/13/bits/stl_construct.h:119
5:     #5 0x7c57ac3c196d in void std::allocator_traits<std::allocator<void> >::construct<mqtt::delivery_token, mqtt::iasync_client&, std::shared_ptr<mqtt::message const>&>(std::allocator<void>&, mqtt::delivery_token*, mqtt::iasync_client&, std::shared_ptr<mqtt::message const>&) /usr/lib/gcc/x86_64-linux-gnu/13/../../../../include/c++/13/bits/alloc_traits.h:661
5:     #6 0x7c57ac3c196d in std::_Sp_counted_ptr_inplace<mqtt::delivery_token, std::allocator<void>, (__gnu_cxx::_Lock_policy)2>::_Sp_counted_ptr_inplace<mqtt::iasync_client&, std::shared_ptr<mqtt::message const>&>(std::allocator<void>, mqtt::iasync_client&, std::shared_ptr<mqtt::message const>&) /usr/lib/gcc/x86_64-linux-gnu/13/../../../../include/c++/13/bits/shared_ptr_base.h:604
5:     #7 0x7c57ac3c18cc in std::__shared_count<(__gnu_cxx::_Lock_policy)2>::__shared_count<mqtt::delivery_token, std::allocator<void>, mqtt::iasync_client&, std::shared_ptr<mqtt::message const>&>(mqtt::delivery_token*&, std::_Sp_alloc_shared_tag<std::allocator<void> >, mqtt::iasync_client&, std::shared_ptr<mqtt::message const>&) /usr/lib/gcc/x86_64-linux-gnu/13/../../../../include/c++/13/bits/shared_ptr_base.h:972
5:     #8 0x7c57ac3beb25 in std::__shared_ptr<mqtt::delivery_token, (__gnu_cxx::_Lock_policy)2>::__shared_ptr<std::allocator<void>, mqtt::iasync_client&, std::shared_ptr<mqtt::message const>&>(std::_Sp_alloc_shared_tag<std::allocator<void> >, mqtt::iasync_client&, std::shared_ptr<mqtt::message const>&) /usr/lib/gcc/x86_64-linux-gnu/13/../../../../include/c++/13/bits/shared_ptr_base.h:1712
5:     #9 0x7c57ac3beb25 in std::shared_ptr<mqtt::delivery_token>::shared_ptr<std::allocator<void>, mqtt::iasync_client&, std::shared_ptr<mqtt::message const>&>(std::_Sp_alloc_shared_tag<std::allocator<void> >, mqtt::iasync_client&, std::shared_ptr<mqtt::message const>&) /usr/lib/gcc/x86_64-linux-gnu/13/../../../../include/c++/13/bits/shared_ptr.h:464
5:     #10 0x7c57ac3beb25 in std::shared_ptr<std::enable_if<!is_array<mqtt::delivery_token>::value, mqtt::delivery_token>::type> std::make_shared<mqtt::delivery_token, mqtt::iasync_client&, std::shared_ptr<mqtt::message const>&>(mqtt::iasync_client&, std::shared_ptr<mqtt::message const>&) /usr/lib/gcc/x86_64-linux-gnu/13/../../../../include/c++/13/bits/shared_ptr.h:1009
5:     #11 0x7c57ac3beb25 in mqtt::delivery_token::create(mqtt::iasync_client&, std::shared_ptr<mqtt::message const>) /tmp/fsw-cmake/deps/Linux-x86_64-6.11.0-1012-oem-Ninja-Clang-19.1.7-lld/paho_mqtt_cpp-v1.5.0/paho_mqtt_cpp-src/include/mqtt/delivery_token.h:102
5:     #12 0x7c57ac3beb25 in mqtt::async_client::publish(std::shared_ptr<mqtt::message const>) /home/fzonta/Projects/fsw-workflow-manager/build//tmp/fsw-cmake/deps/Linux-x86_64-6.11.0-1012-oem-Ninja-Clang-19.1.7-lld/paho_mqtt_cpp-v1.5.0/paho_mqtt_cpp-src/src/async_client.cpp:596
5:     #13 0x7c57ac3ba57a in mqtt::client::publish(std::shared_ptr<mqtt::message const>) /tmp/fsw-cmake/deps/Linux-x86_64-6.11.0-1012-oem-Ninja-Clang-19.1.7-lld/paho_mqtt_cpp-v1.5.0/paho_mqtt_cpp-src/include/mqtt/client.h:296

the crash happens here:

    const string& get_topic() const {
        static const string EMPTY_STR; // <-- here
        return topic_ ? topic_.str() : EMPTY_STR;
    }

by replacing the static variable with a class variable, the segfault disappears. Note that I get this only with clang (version 19.1.7, linker LLD), and with some configurations only.

Do you have any suggestions?

I can try to create a more complete test that replicate the ctash if needed