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[PWGHF] Protect daughter index access in selectEvent to prevent segmentation faults #2281

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Merged
alcaliva merged 2 commits into from
Feb 26, 2026
Merged

[PWGHF] Protect daughter index access in selectEvent to prevent segmentation faults #2281

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[PWGHF] Protect daughter index access in selectEvent to prevent segme…
alcaliva Feb 25, 2026
f385e9a
add library
alcaliva Feb 25, 2026
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40 changes: 34 additions & 6 deletions MC/config/PWGHF/external/generator/generator_pythia8_hfhadron_to_nuclei.C
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@
#include "Pythia8/Pythia.h"
#include "TRandom.h"
#include <fairlogger/Logger.h>
#include <algorithm>
#include <string>
#include <vector>

Expand Down Expand Up @@ -119,18 +120,45 @@ class GeneratorPythia8HFHadToNuclei : public o2::eventgen::GeneratorPythia8
int id = std::abs(event[iPart].id());
float rap = event[iPart].y();
if (id == mHadronPdg && rap > mHadRapidityMin && rap < mHadRapidityMax) {

int d1 = event[iPart].daughter1();
int d2 = event[iPart].daughter2();

// Protection for invalid index of daughter 1
if (d1 < 0 || d1 >= event.size()) {
LOG(info) << "Invalid daughter index 1! d1 = " << d1;
continue;
}

// Protection for invalid index of daughter 2
if (d2 < 0 || d2 >= event.size()) {
LOG(info) << "Invalid daughter index 2! d2 = " << d2;
continue;
}

// Swap order
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@stefanopolitano stefanopolitano Feb 26, 2026

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Hi @alcaliva ! Thanks for the update! I don't have any major comment. Just for my understanding though, does it really happens to have unsorted daughter indices? If I am not mistaken, the first and last daughter indices correspond to the first and last daughter index in the decay tree

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@alcaliva alcaliva Feb 26, 2026

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Hi @stefanopolitano,
honestly, I don't know. I've seen this kind of protection in other codes so I decided to include it also here.
If it doesn't happen, it should be harmless.

if (d1 > d2) {
std::swap(d1, d2);
}

// No daughters
if (d1 == 0 && d2 == 0) {
LOG(info) << "No daughters (0,0). Skipping.";
continue;
}

LOG(debug) << "-----------------------------------------------------";
LOG(debug) << "Found hadron " << event[iPart].id() << " with rapidity " << rap << " and daughters " << event[iPart].daughter1() << " " << event[iPart].daughter2();
LOG(debug) << "Found hadron " << event[iPart].id() << " with rapidity " << rap << " and daughters " << d1 << " " << d2;
// print pdg code of daughters
LOG(debug) << "Daughters: ";
for (int iDau = event[iPart].daughter1(); iDau <= event[iPart].daughter2(); ++iDau) {
for (int iDau = d1; iDau <= d2; ++iDau) {
LOG(debug) << "Daughter " << iDau << ": " << event[iDau].id();
}
bool isCoalDone = CoalescencePythia8(event, mNucleiPdgList, mTrivialCoal, mCoalMomentum, event[iPart].daughter1(), event[iPart].daughter2());
bool isCoalDone = CoalescencePythia8(event, mNucleiPdgList, mTrivialCoal, mCoalMomentum, d1, d2);
if (isCoalDone) {
LOG(debug) << "Coalescence process found for hadron " << event[iPart].id() << " with daughters " << event[iPart].daughter1() << " " << event[iPart].daughter2();
LOG(debug) << "Coalescence process found for hadron " << event[iPart].id() << " with daughters " << d1 << " " << d2;
LOG(debug) << "Check updated daughters: ";
for (int iDau = event[iPart].daughter1(); iDau <= event[iPart].daughter2(); ++iDau) {
for (int iDau = d1; iDau <= d2; ++iDau) {
LOG(debug) << "Daughter " << iDau << ": " << event[iDau].id();
}
return true;
Expand Down Expand Up @@ -171,4 +199,4 @@ FairGenerator *generateHFHadToNuclei(int input_trigger_ratio = 5, std::vector<in
myGen->readString("Random:setSeed on");
myGen->readString("Random:seed " + std::to_string(seed));
return myGen;
}
}