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UBSAN: avoid int overflow in GenHFHadronMatcher #50891

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UBSAN: avoid int overflow in GenHFHadronMatcher #50891

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3 changes: 2 additions & 1 deletion PhysicsTools/JetMCAlgos/plugins/GenHFHadronMatcher.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -979,7 +979,8 @@ int GenHFHadronMatcher::findInMothers(int idx,
}
int pdg_2 = hadMothers[idx2].pdgId();
// Inverting the flavour if bb oscillation detected
if (isHadronPdgId(pdgId, pdg_1) && isHadronPdgId(pdgId, pdg_2) && pdg_1 * pdg_2 < 0) {
if (isHadronPdgId(pdgId, pdg_1) && isHadronPdgId(pdgId, pdg_2) &&
((pdg_1 < 0 && pdg_2 > 0) || (pdg_1 > 0 && pdg_2 < 0))) {
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@Dr15Jones Dr15Jones May 6, 2026

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Another option would be
std::signbit(pdg_1) xor std::signbit(pdg_2)

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@smuzaffar smuzaffar May 6, 2026

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@Dr15Jones , I think std::signbit(pdg_1) xor std::signbit(pdg_2) might not work if one of these variables hold 0

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@Dr15Jones Dr15Jones May 6, 2026

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Agreed, but 0 is not a valid value for a PDG id (according to my internet search). Therefore no particle is ever supposed to have that value.

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@smuzaffar smuzaffar May 6, 2026

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ah ok, in that case ((pdg_1 < 0) != (pdg_2 < 0)) should be enough but may be then we should add assert to make sure values are not zero

pdgId *= -1;
if (verbose)
printf("######### Inverting flavour of the hadron\n");
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