June 2025 - Boost-users - lists.boost.org

Issue with Python 3.12 and Concurrent Threads
by jholbrook＠kinetic-vision.com 19 Jun '25

19 Jun '25

Hi, I have a Windows application that has been using Boost Python for many years now, and we are looking to upgrade from Python 3.7 to Python 3.12. This is a C++ application written in Qt5 that uses Boost Python to interface with Python scripts that do some scientific calculations, and the results are displayed in the C++ application. As such, these calculations are by and large done on a concurrent thread so as not to block the UI; however, some quick python functions are run from the main thread. The problem is that *something* changed in the Python 3.12 upgrade, and I'm not sure what -- but now it crashes when I run Python code from a different thread from the one I called Py_Initialize() on. I've tested up to Python 3.11, and I can Py_Initialize() on the main thread and call Python code from any thread and everything works. But starting in Python 3.12, that's no longer the case. If I initialize Python on the UI thread, I can only run it from that thread. If I initialize it on a concurrent thread, I can only run it on a concurrent thread. Since I am using Python, Qt5, and Boost Python, I am not 100% sure where the fault lies, but I am posting this here in case anyone has run into this issue. I haven't found any other references to it online. I can post a minimal example project if that would be helpful for debugging. Essentially, this is the meat of my code: //Initialization Function: Py_Initialize(); //Boost Python Code: boost::python::object main = boost::python::import("__main__"); boost::python::object name_space(main.attr("__dict__")); boost::python::exec_file("testPython.py", name_space, name_space); double testNumber = boost::python::extract<double>(name_space["testNumber"]); qDebug() << testNumber; //print(testNumber) #testPython.py: import random testNumber = random.random() Thanks for any help you can provide.

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Issue with Python 3.12 and Concurrent Threads
by jholbrook＠kinetic-vision.com 18 Jun '25

18 Jun '25

Hi, I have a Windows application that has been using Boost Python for many years now, and we are looking to upgrade from Python 3.7 to Python 3.12. This is a C++ application written in Qt5 that uses Boost Python to interface with Python scripts that do some scientific calculations, and the results are displayed in the C++ application. As such, these calculations are by and large done on a concurrent thread so as not to block the UI; however, some quick python functions are run from the main thread. The problem is that *something* changed in the Python 3.12 upgrade, and I'm not sure what -- but now it crashes when I run Python code from a different thread from the one I called Py_Initialize() on. I've tested up to Python 3.11, and I can Py_Initialize() on the main thread and call Python code from any thread and everything works. But starting in Python 3.12, that's no longer the case. If I initialize Python on the UI thread, I can only run it from that thread. If I initialize it on a concurrent thread, I can only run it on a concurrent thread. Since I am using Python, Qt5, and Boost Python, I am not 100% sure where the fault lies, but I am posting this here in case anyone has run into this issue. I haven't found any other references to it online. I can post a minimal example project if that would be helpful for debugging. Essentially, this is the meat of my code: //Initialization Function: Py_Initialize(); //Boost Python Code: boost::python::object main = boost::python::import("__main__"); boost::python::object name_space(main.attr("__dict__")); boost::python::exec_file("testPython.py", name_space, name_space); double testNumber = boost::python::extract<double>(name_space["testNumber"]); qDebug() << testNumber; //print(testNumber) #testPython.py: import random testNumber = random.random() Thanks for any help you can provide.

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Assignment of boost::dll::import_symbol to boost::shared_ptr fails to compile
by Yuri 14 Jun '25

14 Jun '25

I've encountered the compilation error with this program with boost-libs-1.88.0: #include <boost/dll/import.hpp> #include <boost/shared_ptr.hpp> class API { public: API() { } }; void x() { boost::shared_ptr<API> pluginInterface; pluginInterface = boost::dll::import_symbol<API>("path", "name"); } The error: $ c++ -std=c++20 -c s.cpp -I /usr/local/include/ s.cpp:13:21: error: no viable overloaded '=' 13 | pluginInterface = boost::dll::import_symbol<API>("path", "name"); | ~~~~~~~~~~~~~~~ ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ /usr/local/include/boost/smart_ptr/shared_ptr.hpp:407:18: note: candidate function not viable: no known conversion from 'boost::dll::detail::import_type<API>' (aka 'st d::shared_ptr<API>') to 'const shared_ptr<API>' for 1st argument 407 | shared_ptr & operator=( shared_ptr const & r ) noexcept | ^ ~~~~~~~~~~~~~~~~~~~~ Compiler: clang-19, but gcc-12 fails in a similar way. It seems that such assignment should work. This error was originally found in the Dakota project (https://github.com/snl-dakota/dakota) This error prevents the Dakota project from compiling. Thanks, Yuri

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mailman upgrade
by Sam Darwin 04 Jun '25

04 Jun '25

Hi, As discussed earlier on the developer list, mailman2 is end-of-life and no longer supported. We are planning to upgrade the mailing lists from mailman2 to mailman3. This will be done in-place, importing the previous archives and user list into a mm3 instance hosted at the same URL lists.boost.org. An example staging instance can be viewed at https://lists.preview.boost.org Mailman3 is more complex than Mailman2 with multiple components including "web" and "core". After the upgrade your account should still exist in the core backend, which means you will continue to receive messages and be able to send emails. However, to interact with the web frontend (optional) you must register an account using the same email address at https://lists.boost.org. Registering in the web portal will require setting up a new password, and confirming the email address. Be sure to use your existing email from before. Any previous passwords will not be valid. If you don't create an account in the web UI, your email subscriptions to the lists continue. But you can't yet log in to configure the account. No action is needed right now. Wait until after the upgrade. All previous messages will be imported to the new system. Additionally, the earlier archives in the form of static plain html pages will be available at https://listarchives.boost.org/ The imported lists are Boost, Boost Announce, and Boost Users. Activity on any other lists is remarkably low such as 1-2 emails per year. Please migrate other discussions to Github Issues, Slack, or one of the main mailing lists. Let us know any concerns. Report issues in the github repository cppalliance/boost-mailman. The tentative schedule is Tuesday June 17. Plan on not using the list for one day, or perhaps a few days. Roll back to mailman2 if something unusual is discovered soon after going live. Chat out-of-band in cpplang slack boost channel.

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boost::process v1 broken in 1_88_0
by Sebastian Koerner 02 Jun '25

02 Jun '25

Hi Boost-Users, I understand that boost process has v2 and v1 is deprecated, but I thought v1 will at least work on for existing stuff. Between 1_87 and 1_88 process v1 stopped working with v1 code. Something changed v1-incompatible with the includes, like: boost::process::child is unknown. error: ‘child’ is not a member of ‘boost::process’ 73 | std::vector<boost::process::child> m_processes; Is this known or easy-to fix?

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