The global operator override new looks unsafe.

[AndreaCatania]

Hello, while integrating a library based on the Jolt Physics; I've noticed that it uses new to create the Body objects https://github.com/jrouwe/JoltPhysics/blob/master/Jolt/Physics/Body/BodyManager.cpp#L148-L157.
Therefore, the new operator can be overridden to provide a custom allocator, to eventually support linear allocation.

The issue is that the global-override-new is not confined into the library, rather it s global per executable. It means that the rest of the application, where my library will be used, will also use the new defined by my library: this is unsafe and undesired.

I wonder if would be possible to switch to an Allocator solution, instead to rely on new.

Please, let me know if my understanding on how it works is wrong.

[mihe]

(I'm not a Jolt developer, just some random user of Jolt.)

Jolt overrides the new and delete operators per-class (i.e. not globally) using this macro:

JoltPhysics/Jolt/Core/Memory.h

Lines 28 to 37 in ad9cd40

	/// Macro to override the new and delete functions
	#define JPH_OVERRIDE_NEW_DELETE \
	JPH_INLINE void *operator new (size_t inCount) { return JPH::Allocate(inCount); } \
	JPH_INLINE void operator delete (void *inPointer) noexcept { JPH::Free(inPointer); } \
	JPH_INLINE void *operator new[] (size_t inCount) { return JPH::Allocate(inCount); } \
	JPH_INLINE void operator delete[] (void *inPointer) noexcept { JPH::Free(inPointer); } \
	JPH_INLINE void *operator new (size_t inCount, std::align_val_t inAlignment) { return JPH::AlignedAllocate(inCount, static_cast<size_t>(inAlignment)); } \
	JPH_INLINE void operator delete (void *inPointer, std::align_val_t inAlignment) noexcept { JPH::AlignedFree(inPointer); } \
	JPH_INLINE void *operator new[] (size_t inCount, std::align_val_t inAlignment) { return JPH::AlignedAllocate(inCount, static_cast<size_t>(inAlignment)); } \
	JPH_INLINE void operator delete[] (void *inPointer, std::align_val_t inAlignment) noexcept { JPH::AlignedFree(inPointer); }

Which you'll find is used in Body here:

JoltPhysics/Jolt/Physics/Body/Body.h

Lines 32 to 35 in ad9cd40

	class alignas(JPH_RVECTOR_ALIGNMENT) JPH_EXPORT Body : public NonCopyable
	{
	public:
	JPH_OVERRIDE_NEW_DELETE

The functions that are used in this macro can be set by the user through these global function pointers:

JoltPhysics/Jolt/Core/Memory.h

Lines 19 to 23 in ad9cd40

	// User defined allocation / free functions
	JPH_EXPORT extern AllocateFunction Allocate;
	JPH_EXPORT extern FreeFunction Free;
	JPH_EXPORT extern AlignedAllocateFunction AlignedAllocate;
	JPH_EXPORT extern AlignedFreeFunction AlignedFree;

Which in examples like HelloWorld is typically done using this function, which defaults them to malloc/free and its aligned equivalents:

JoltPhysics/Jolt/Core/Memory.cpp

Lines 63 to 69 in ad9cd40

	void RegisterDefaultAllocator()
	{
	Allocate = AllocateImpl;
	Free = FreeImpl;
	AlignedAllocate = AlignedAllocateImpl;
	AlignedFree = AlignedFreeImpl;
	}

You can find an example of me hooking up mimalloc to Jolt here.

[AndreaCatania]

Nice, this is much cleaner now, thx!