Question: exception mismatch reported by lcov in pytypes.h #5573

Hello,

The matplotlib charting library uses pybind11, and also uses GitHub Actions to run gcov and lcov -- code coverage utilities.

After upgrading the GitHub Actions runner images in matplotlib/matplotlib#29765 (to allow installation of a recently-required dependency), the updated versions of those utilities resulted in a report of a mismatch in the pytypes.h header file. Specifically, that an object-to-string conversion method declared in a macro there appeared to have mismatched exception-related behaviour:

geninfo: ERROR: "/opt/hostedtoolcache/Python/3.12.9/x64/lib/python3.12/site-packages/pybind11/include/pybind11/pytypes.h":1562: mismatched exception tag for id 1, 1: '1' -> '0'

The macro callsite appears to be this one:

Question
I'd prefer not to disable/ignore this warning without knowing whether it is reporting a geuine problem, or whether it is a bug in gcov/lcov, or a false positive for some reason. Does anyone here have experience with this who can identify what the problem is?

Thank you!