Structs and the GC

[Mark SiblyKeymaster]

Strings are allocated from the heap, but are reference counted instead of GC’d.

[sicilicaParticipant]

In case anyone searches into this thread later with a similar situation, a solution like this should work:

Monkey

Import "<libc>" Using libc.. Struct Vec3     Property X:Float()         Return data[0]     Setter(val:Float)         data[0] = val     End     Property Y:Float()         Return data[1]     Setter(val:Float)         data[1] = val     End     Property Z:Float()         Return data[2]     Setter(val:Float)         data[2] = val     End     Field data:Float Ptr     Const SIZE = 12    ' 3 floats, 4 bytes each End Function Vec3_Alloc(out:Vec3 Ptr, count:Int = 1)     Local mem:Byte Ptr = malloc(count * Vec3.SIZE)     ' this assignment work depends on your specific struct     ' probably need to do array syntax into mem, since pointer arithmetic isn't allowed?     For Local i = 0 Until count         out[i].data = Varptr mem[i * Vec3.SIZE]     Next End Function Vec3_Free(val:Vec3 Ptr)     ' this depends on your specific struct     ' free whatever you had at mem[0], if you have multiple fields in the struct     free(val.data) End

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43

Import "<libc>"   Using libc..   Struct Vec3       Property X:Float()         Return data[0]     Setter(val:Float)         data[0] = val     End     Property Y:Float()         Return data[1]     Setter(val:Float)         data[1] = val     End     Property Z:Float()         Return data[2]     Setter(val:Float)         data[2] = val     End       Field data:Float Ptr       Const SIZE = 12    ' 3 floats, 4 bytes each   End   Function Vec3_Alloc(out:Vec3 Ptr, count:Int = 1)     Local mem:Byte Ptr = malloc(count * Vec3.SIZE)       ' this assignment work depends on your specific struct     ' probably need to do array syntax into mem, since pointer arithmetic isn't allowed?     For Local i = 0 Until count         out[i].data = Varptr mem[i * Vec3.SIZE]     Next End   Function Vec3_Free(val:Vec3 Ptr)     ' this depends on your specific struct     ' free whatever you had at mem[0], if you have multiple fields in the struct     free(val.data) End

Vec3_Alloc() can allocate arrays of contiguous memory for storing a large number structs.

Your struct should only contain pointers if you do this (even, say, a single float needs to be a pointer; classes are fine, since they are always be pointers, but ofc they shouldn’t be allocated from your malloc memory).

If you allocate an array of structs, they have to all be free’d at once, pass a pointer to the first one to the Vec3_Free() function (duh).

You still need to store your ACTUAL structs somewhere on the heap, so they are technically separate from the memory, eg:

Monkey

Global triangle:= New Vec3[3] ' this is telling the GC where the actual structs themselves are, use pointers everywhere except here Vec3_Allocate(Varptr triangle, 3)

1 2	Global triangle:= New Vec3[3] ' this is telling the GC where the actual structs themselves are, use pointers everywhere except here Vec3_Allocate(Varptr triangle, 3)

And as the last caveat, you’ll fracture your memory a lot worse than even the GC would if you don’t know what you’re doing, so for example, don’t actually create a single triangle this way.

[sicilicaParticipant]

Here’s a much better example.

Monkey

Function Mesh_Alloc(mesh:Mesh Ptr, numVertices:Int, numTriangles:Int) mesh->numVertices = numVertices mesh->numTriangles = numTriangles Local mem:Byte Ptr = Cast<Byte Ptr>(malloc(numVertices*Vertex.SIZE + numTriangles*Triangle.SIZE)) mesh->vertices = Cast<Vertex Ptr>(mem) mesh->triangles = Cast<Triangle Ptr>(Varptr mem[numVertices*Vertex.SIZE]) End Function Mesh_Free(mesh:Mesh Ptr) free(mesh->vertices) mesh->numVertices = 0 mesh->numTriangles = 0 mesh->vertices = Null mesh->triangles = Null End Struct Mesh Field numVertices:Int Field vertices:Vertex Ptr Field numTriangles:Int Field triangles:Triangle Ptr End Struct Vertex Field texCoords:Vec2f Field position:Vec3f Const SIZE:= 2*SIZE_OF_FLOAT + 3*SIZE_OF_FLOAT End Struct Triangle Field vertexIndex0:Short Field vertexIndex1:Short Field vertexIndex2:Short Const SIZE:= 3*SIZE_OF_SHORT End Const SIZE_OF_SHORT:= 2 Const SIZE_OF_FLOAT:= 4

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49

Function Mesh_Alloc(mesh:Mesh Ptr, numVertices:Int, numTriangles:Int) mesh->numVertices = numVertices mesh->numTriangles = numTriangles   Local mem:Byte Ptr = Cast<Byte Ptr>(malloc(numVertices*Vertex.SIZE + numTriangles*Triangle.SIZE)) mesh->vertices = Cast<Vertex Ptr>(mem) mesh->triangles = Cast<Triangle Ptr>(Varptr mem[numVertices*Vertex.SIZE]) End Function Mesh_Free(mesh:Mesh Ptr) free(mesh->vertices)   mesh->numVertices = 0 mesh->numTriangles = 0 mesh->vertices = Null mesh->triangles = Null End   Struct Mesh   Field numVertices:Int Field vertices:Vertex Ptr Field numTriangles:Int Field triangles:Triangle Ptr   End       Struct Vertex   Field texCoords:Vec2f Field position:Vec3f   Const SIZE:= 2*SIZE_OF_FLOAT + 3*SIZE_OF_FLOAT   End Struct Triangle   Field vertexIndex0:Short Field vertexIndex1:Short Field vertexIndex2:Short   Const SIZE:= 3*SIZE_OF_SHORT   End   Const SIZE_OF_SHORT:= 2 Const SIZE_OF_FLOAT:= 4

[Author]

Posts