adds gc_disable/gc_enable to allow delaying GC of python objects

Author: Christopher Doris

src/Py.jl

@@ -43,13 +43,7 @@ mutable struct Py
 end
 export Py
 
-function py_finalizer(x::Py)
-    if C.CTX.is_initialized
-        C.with_gil(false) do
-            C.Py_DecRef(getptr(x))
-        end
-    end
-end
+py_finalizer(x::Py) = C.gc_enqueue(getptr(x))
 
 ispy(::Py) = true
 getptr(x::Py) = getfield(x, :ptr)

src/cpython/CPython.jl

@@ -16,6 +16,7 @@ include("extras.jl")
 include("context.jl")
 include("gil.jl")
 include("jlwrap.jl")
+include("gc.jl")
 
 function __init__()
     init_context()

src/cpython/gc.jl

@@ -0,0 +1,52 @@
+const GC_ENABLED = Ref(true)
+const GC_QUEUE = PyPtr[]
+
+function gc_disable()
+    GC_ENABLED[] = false
+    return
+end
+
+function gc_enable()
+    GC_ENABLED[] = true
+    if !isempty(GC_QUEUE)
+        with_gil(false) do
+            for ptr in GC_QUEUE
+                if ptr != PyNULL
+                    Py_DecRef(ptr)
+                end
+            end
+        end
+    end
+    empty!(GC_QUEUE)
+    return
+end
+
+function gc_enqueue(ptr::PyPtr)
+    if ptr != PyNULL && CTX.is_initialized
+        if GC_ENABLED[]
+            with_gil(false) do
+                Py_DecRef(ptr)
+            end
+        else
+            push!(GC_QUEUE, ptr)
+        end
+    end
+    return
+end
+
+function gc_enqueue_all(ptrs)
+    if CTX.is_initialized
+        if GC_ENABLED[]
+            with_gil(false) do
+                for ptr in ptrs
+                    if ptr != PyNULL
+                        Py_DecRef(ptr)
+                    end
+                end
+            end
+        else
+            append!(GC_QUEUE, ptrs)
+        end
+    end
+    return
+end

src/jlwrap/objectarray.jl

@@ -23,15 +23,7 @@ PyObjectArray(undef::UndefInitializer, dims::Vararg{Integer,N}) where {N} = PyOb
 PyObjectArray{N}(x::AbstractArray{T,N}) where {T,N} = copyto!(PyObjectArray{N}(undef, size(x)), x)
 PyObjectArray(x::AbstractArray{T,N}) where {T,N} = PyObjectArray{N}(x)
 
-pyobjectarray_finalizer(x::PyObjectArray) = begin
-    if C.CTX.is_initialized
-        C.with_gil(false) do
-            for ptr in x.ptrs
-                C.Py_DecRef(ptr)
-            end
-        end
-    end
-end
+pyobjectarray_finalizer(x::PyObjectArray) = C.gc_enqueue_all(x.ptrs)
 
 Base.IndexStyle(x) = Base.IndexStyle(x.ptrs)