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aardappel / lobster

The Lobster Programming Language
http://strlen.com/lobster
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Avoid comparing against uninitialized expiration value for particles. #219

Closed stolk closed 1 year ago

stolk commented 1 year ago

Don't use uninitialised expiration values.

The particle system tries to be lazy when setting expiration values. When doing so, it will compare the new value to an uninitialised value. We should set the value to zero, before we ever compare to it.

==92419== Conditional jump or move depends on uninitialised value(s)
==92419==    at 0xBFF5C5: b2ParticleSystem::SetParticleLifetime(int, float) (dev/include/Box2D/Particle/b2ParticleSystem.cpp:4255)
==92419==    by 0xBFE831: b2ParticleSystem::CreateParticle(b2ParticleDef const&) (dev/include/Box2D/Particle/b2ParticleSystem.cpp:718)
==92419==    by 0xC0045A: b2ParticleSystem::CreateParticleForGroup(b2ParticleGroupDef const&, b2Transform const&, b2Vec2 const&) (dev/include/Box2D/Particle/b2ParticleSystem.cpp:876)
==92419==    by 0xC007D0: b2ParticleSystem::CreateParticlesFillShapeForGroup(b2Shape const*, b2ParticleGroupDef const&, b2Transform const&) (dev/include/Box2D/Particle/b2ParticleSystem.cpp:937)
==92419==    by 0xC00884: b2ParticleSystem::CreateParticlesWithShapeForGroup(b2Shape const*, b2ParticleGroupDef const&, b2Transform const&) (dev/include/Box2D/Particle/b2ParticleSystem.cpp:954)
==92419==    by 0xC00A25: b2ParticleSystem::CreateParticleGroup(b2ParticleGroupDef const&) (dev/include/Box2D/Particle/b2ParticleSystem.cpp:1062)
==92419==    by 0x98DEFB: AddPhysics(lobster::NativeRegistry&)::$_14::operator()(lobster::Value*&, lobster::VM&) const (dev/src/physics.cpp:302)
==92419==    by 0x98DD6C: AddPhysics(lobster::NativeRegistry&)::$_14::__invoke(lobster::Value*&, lobster::VM&) (dev/src/physics.cpp:292)
==92419==    by 0x9D064E: lobster::U_BCALLRETV(lobster::VM&, lobster::Value*, int, int) (dev/src/lobster/vmops.h:269)
==92419==    by 0x9D0605: CVM_BCALLRETV (dev/src/vm.cpp:813)
==92419==    by 0x5F14DD7: ???
==92419==    by 0x5F15D9C: ???
==92419==  Uninitialised value was created by a heap allocation
==92419==    at 0x4848899: malloc (in /usr/libexec/valgrind/vgpreload_memcheck-amd64-linux.so)
==92419==    by 0xBDB167: b2AllocDefault(int, void*) (dev/include/Box2D/Common/b2Settings.cpp:58)
==92419==    by 0xBDB1C0: b2Alloc(int) (dev/include/Box2D/Common/b2Settings.cpp:96)
==92419==    by 0xBDB8D8: b2TrackedBlock::Allocate(unsigned int) (dev/include/Box2D/Common/b2TrackedBlock.cpp:55)
==92419==    by 0xBDB9CE: b2TrackedBlockAllocator::Allocate(unsigned int) (dev/include/Box2D/Common/b2TrackedBlock.cpp:93)
==92419==    by 0xBDA0FD: b2BlockAllocator::Allocate(int) (dev/include/Box2D/Common/b2BlockAllocator.cpp:114)
==92419==    by 0xC12503: int* b2ParticleSystem::ReallocateBuffer<int>(int*, int, int) (dev/include/Box2D/Particle/b2ParticleSystem.cpp:489)
==92419==    by 0xC124BB: int* b2ParticleSystem::ReallocateBuffer<int>(int*, int, int, int, bool) (dev/include/Box2D/Particle/b2ParticleSystem.cpp:515)
==92419==    by 0xC0EF44: int* b2ParticleSystem::ReallocateBuffer<int>(b2ParticleSystem::UserOverridableBuffer<int>*, int, int, bool) (dev/include/Box2D/Particle/b2ParticleSystem.cpp:526)
==92419==    by 0xBFE415: b2ParticleSystem::ReallocateInternalAllocatedBuffers(int) (dev/include/Box2D/Particle/b2ParticleSystem.cpp:631)
==92419==    by 0xBFE52B: b2ParticleSystem::CreateParticle(b2ParticleDef const&) (dev/include/Box2D/Particle/b2ParticleSystem.cpp:654)
==92419==    by 0xC0045A: b2ParticleSystem::CreateParticleForGroup(b2ParticleGroupDef const&, b2Transform const&, b2Vec2 const&) (dev/include/Box2D/Particle/b2ParticleSystem.cpp:876)
aardappel commented 1 year ago

The particle system is from this upstream: https://github.com/google/liquidfun So ideally it would have to be fixed there, but pretty sure it is effectively abandoned (I used to work on that team).

Don't mind fixing it here also, given that those files are unlikely to be updated at the source, but worth opening an issue/PR there too just in case someone at Google is still listening :)