lcov fails with gcc 14

[Klaus33333]

lcov fails with gcc 14

[henry2cox]

I fear that I'm not entirely sure which fixes/workarounds you are looking for.
It appears that we see two different errors/inconsistencies in the gcov data for this testcase:

1. function _ZN17TEST1_SUITE1_Test8TestBodyEv is found to end on line .../test1.cpp:9 in one GCDA file but is found to end on line 19 in another file.
   This appears to be a bug in gcov (or in gcc) which turns up sometimes (...which is why lcov checks for it).
   lcov uses the function range to figure out which coverpoints belong to the function, in order to support function-level exclusion and also to report covered proportions.
   You can safely ignore the error if you don't care about those features.
   To work around it is a bit painful - as you would have to manually fix the start/end lines (e.g., via sed on the data file)...or possibly someone can fix it in gcc/gcov.

2. The gcov output data is not consistent at line file1.c:2811.
   I fear that I have forgotten the details, but the comment near line geninfo:2324 suggests that the report will look weird because we will see a block inside some conditional (say, the 'if' clause) such that the 'if' expression is not evaluated but the statement is hit.
   The suggested workaround is to tell geninfo to set the block hit count to zero when that happens (or gcc/gcov need to fix the bug).
   To see how the second issue affects your coverage report: capture your coverage data twice - once setting the count and once without, then generate a differential coverage report (genhtml -o whatTheHeck --baseline-file without.info with.info ...) and inspect the differences.