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[Python] Move the PyROOT application setup to Python - #23699
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guitargeek merged 2 commits intoOct 13, 2026
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PyROOT turns ROOT warnings into Python warnings with an error handler in its CPython extension module. It must not take the GIL while ROOT runs multithreaded: the reporting thread may hold ROOT's lock, which a thread holding the GIL may be waiting for. That check has to run before any Python code, so it can't move to Python with the rest of the handler. SetWarningHandler() installs an error handler that does the check and passes warnings to a plain function pointer. The handler returns whether it took the warning, so the Python bindings can decline one while a Python exception is pending; declined warnings go to DefaultErrorHandler() like every other message. 🤖 Done with the help of AI
RPyROOTApplication.cxx created the TApplication from the command line options, set up ROOT globals, and installed the error handler that turns ROOT warnings into Python warnings and the PyOS_InputHook that processes GUI events while the Python prompt waits for input. The TApplication is now constructed in _application.py through cppyy, with the same options from sys.argv; its constructor already saves the interpreter context, which the subclass did a second time. Of the ROOT globals only gBenchmark still needs setting: TROOT builds gStyle and TApplication sets gProgName, and evaluating gStyle created the proxies of TStyle and its base classes during every import. The warning handler and the input hook stay compiled, in PyROOTModule.cxx: - a Python callable passed to ROOT::Internal::SetWarningHandler() makes cppyy compile a trampoline during every import, which parses Python.h and takes half a second. The handler now declines warnings while a Python exception is pending, e.g. after a previous warning turned into an error in the same C++ call: PyErr_WarnExplicit() then replaced the exception with a SystemError. - a ctypes callback as input hook swallows the KeyboardInterrupt of a Ctrl-C arriving while it runs, so the Ctrl-C is lost. The setup runs while the ROOT module is being set up, so it goes through cppyy.gbl rather than the ROOT module, and the pythonization decorator test excludes the classes it now creates proxies of. 🤖 Done with the help of AI
guitargeek
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pcanal,
siliataider and
vepadulano
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October 13, 2026 09:33
vepadulano
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Oct 13, 2026
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Thanks! See one minor comment.
Test Results 24 files 24 suites 4d 3h 54m 51s ⏱️ For more details on these failures, see this check. Results for commit 51efb9c. ♻️ This comment has been updated with latest results. |
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