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[LTO_X - Alignment & Calibration] Solve -Wstrict-overflow compiler warnings #38649

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[LTO_X - Alignment & Calibration] Solve -Wstrict-overflow compiler warnings #38649

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2 changes: 1 addition & 1 deletion Alignment/OfflineValidation/plugins/OverlapValidation.cc
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Expand Up @@ -383,7 +383,7 @@ void OverlapValidation::analyzeTrajectory(const Trajectory& trajectory,
++overlapCounts_[1];
if ((layer != -1) && (acceptLayer[subDet])) {
for (vector<TrajectoryMeasurement>::const_iterator itmCompare = itm - 1;
itmCompare >= measurements.begin() && itmCompare > itm - 4;
(itmCompare >= measurements.begin()) && ((itmCompare + 4) > itm);
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I'd argue comparing an iterator to be larger than or equal with begin() does not make much sense as in principle it is always true because

The begin iterator is not decrementable and the behavior is undefined if --container.begin() is evaluated.

https://en.cppreference.com/w/cpp/named_req/BidirectionalIterator

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but itm-1 has a similar issue when itm is equal to measurements.begin(), no? or is that somehow ok?

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but itm-1 has a similar issue when itm is equal to measurements.begin(), no?

Right (didn't look that far), already the itm-1 seems to be potentially undefined behavior.

How about rewriting the loop e.g. along

for (int offset = 1, end=std::min(3, std::distance(measurements.begin(), itm)); offset <= end; ++offset) {
  auto itmCompare = std::prev(itm, offset);
  ...
}

Then, for

  • itm == begin() the loop body would not be run
  • itm == begin()+1 the loop body would be run with itmCompare = itm-1
  • itm == begin()+2 the loop body would be run with itmCompare = itm-1 and itm-2
  • itm >= begin()+3 the loop body would be run with itmCompare = itm-1, itm-2, and itm-3

(I'm sure there are even better ways to write the loop)

--itmCompare) {
DetId compareId = itmCompare->recHit()->geographicalId();

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2 changes: 1 addition & 1 deletion Alignment/TrackerAlignment/plugins/TkAlCaOverlapTagger.cc
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Expand Up @@ -126,7 +126,7 @@ void TkAlCaOverlapTagger::produce(edm::Event& iEvent, const edm::EventSetup& iSe

if ((previousTM != nullptr) && (layer != -1)) {
for (std::vector<TrajectoryMeasurement>::const_iterator itmCompare = itTrajMeas - 1;
itmCompare >= tmColl.begin() && itmCompare > itTrajMeas - 4;
(itmCompare >= tmColl.begin()) && ((itmCompare + 4) > itTrajMeas);
--itmCompare) {
DetId compareId = itmCompare->recHit()->geographicalId();
if (subDet != compareId.subdetId() || layer != layerFromId(compareId, tTopo))
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2 changes: 1 addition & 1 deletion Calibration/Tools/src/HouseholderDecomposition.cc
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Expand Up @@ -442,7 +442,7 @@ void HouseholderDecomposition::solve(std::vector<float>& y) {

for (i = Nchannels - 2; i >= 0; i--) {
z[i] = energyVectorProc[i];
for (j = i + 1; j < Nchannels; j++) {
for (j = i + 1; j - Nchannels < 0; j++) {
z[i] -= eventMatrixProc[i][j] * z[j];
}
z[i] /= alpha[i];
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