Fix bugs in TrkReco: break→continue, division by zero, bounds checks, shadowing, dead code

[Copilot]

Summary

Fixes critical and high-severity bugs in TrkReco identified during code review.

Critical Fixes

break → continue in track matching loops

Files: SelectReflections_module.cc:98, SelectSameTrack_module.cc:116

Both modules had break instead of continue when no intersection was found for a track. The comment says "skip testing for a match with this track", but break terminates the entire outer loop over all tracks, silently skipping all remaining candidates. Changed to continue to correctly advance to the next track.

Missing histogram bounds check in initFZ_2()

File: RobustHelixFit.cc:580

The histogram hist[20] fill loop computed bin = (x-minX)/stepX without bounds checking. The physics range [_mindfdz, _maxdfdz] is user-configurable via fcl but the histogram parameters are hardcoded, creating a fragile coupling that could lead to out-of-bounds writes. Added if(bin >= 0 && bin < int(nbinsX)) guard.

High-Severity Fixes

Division by zero guards

• SimpleKalSeedSelector_tool.cc:32: When both tracks have zero active hits, ntest + ncurrent == 0 produces NaN. Added early fallback to fit consistency comparison.
• SelectSameTrack_module.cc:147: When prihits is empty, nover/prihits.size() divides by zero. Added if(prihits.empty()) continue; guard before the overlap computation.
• TrkUtilities.cc:50: overlap(SHIV) divides by min(size1, size2) which is 0 when either vector is empty. Added early return of 0.0.

Medium-Severity Fixes

• TrackMatching_module.cc:201: Renamed inner ntrks to ntrks_handle to avoid shadowing the outer ntrks used for validation.
• SelectReflections_module.cc:133, SelectSameTrack_module.cc:165: Changed numeric_limits<float>::max() to numeric_limits<double>::max() to match the double variable type.
• RobustHelixFinderData.cc:66-70: Removed duplicate assignments of _nStrawHits, _nComboHits, _nFiltComboHits, _nFiltStrawHits in clearTempVariables().

Files Changed

• TrkReco/src/SelectReflections_module.cc
• TrkReco/src/SelectSameTrack_module.cc
• TrkReco/src/SimpleKalSeedSelector_tool.cc
• TrkReco/src/TrkUtilities.cc
• TrkReco/src/TrackMatching_module.cc
• TrkReco/src/RobustHelixFit.cc
• TrkReco/src/RobustHelixFinderData.cc

[FNALbuild]

Hi @Copilot,
You have proposed changes to files in these packages:

• TrkReco

which require these tests: build.

@Mu2e/write, @Mu2e/fnalbuild-users have access to CI actions on main.

📝 The author of this pull request is not a member of the Mu2e github organisation.

About FNALbuild. Code review on Mu2e/Offline.

[brownd1978]

These look correct or innocuous.

[oksuzian]

@FNALbuild run build test

[FNALbuild]

⌛ The following tests have been triggered for 8fd3bcf: build (Build queue - API unavailable)

[FNALbuild]

☀️ The build tests passed at 8fd3bcf.

Test	Result	Details
test with	✅	Command did not list any other PRs to include
merge	✅	Merged 8fd3bcf at e229837
build (prof)	✅	Log file. Build time: 04 min 08 sec
ceSimReco	✅	Log file.
g4test_03MT	✅	Log file.
transportOnly	✅	Log file.
POT	✅	Log file.
g4study	✅	Log file.
cosmicSimReco	✅	Log file.
cosmicOffSpill	✅	Log file.
ceSteps	✅	Log file.
ceDigi	✅	Log file.
muDauSteps	✅	Log file.
ceMix	✅	Log file.
rootOverlaps	✅	Log file.
g4surfaceCheck	✅	Log file.
trigger	✅	Log file.
check_cmake	✅	Log file.
FIXME, TODO	➡️	TODO (0) FIXME (4) in 7 files
clang-tidy	➡️	9 errors 239 warnings
whitespace check	✅	no whitespace errors found

N.B. These results were obtained from a build of this Pull Request at 8fd3bcf after being merged into the base branch at e229837.

For more information, please check the job page here.
Build artifacts are deleted after 5 days. If this is not desired, select Keep this build forever on the job page.