1 files changed, 108 insertions, 0 deletions
diff --git a/contrib/tools/python3/Python/object_stack.c b/contrib/tools/python3/Python/object_stack.c
new file mode 100644
index 00000000000..bd9696822c8
--- /dev/null
+++ b/contrib/tools/python3/Python/object_stack.c
@@ -0,0 +1,108 @@
+// Stack of Python objects
+
+#include "Python.h"
+#include "pycore_freelist.h"
+#include "pycore_pystate.h"
+#include "pycore_object_stack.h"
+
+extern _PyObjectStackChunk *_PyObjectStackChunk_New(void);
+extern void _PyObjectStackChunk_Free(_PyObjectStackChunk *);
+
+static struct _Py_object_stack_freelist *
+get_object_stack_freelist(void)
+{
+    struct _Py_object_freelists *freelists = _Py_object_freelists_GET();
+    return &freelists->object_stacks;
+}
+
+_PyObjectStackChunk *
+_PyObjectStackChunk_New(void)
+{
+    _PyObjectStackChunk *buf;
+    struct _Py_object_stack_freelist *obj_stack_freelist = get_object_stack_freelist();
+    if (obj_stack_freelist->numfree > 0) {
+        buf = obj_stack_freelist->items;
+        obj_stack_freelist->items = buf->prev;
+        obj_stack_freelist->numfree--;
+    }
+    else {
+        // NOTE: we use PyMem_RawMalloc() here because this is used by the GC
+        // during mimalloc heap traversal. In that context, it is not safe to
+        // allocate mimalloc memory, such as via PyMem_Malloc().
+        buf = PyMem_RawMalloc(sizeof(_PyObjectStackChunk));
+        if (buf == NULL) {
+            return NULL;
+        }
+    }
+    buf->prev = NULL;
+    buf->n = 0;
+    return buf;
+}
+
+void
+_PyObjectStackChunk_Free(_PyObjectStackChunk *buf)
+{
+    assert(buf->n == 0);
+    struct _Py_object_stack_freelist *obj_stack_freelist = get_object_stack_freelist();
+    if (obj_stack_freelist->numfree >= 0 &&
+        obj_stack_freelist->numfree < _PyObjectStackChunk_MAXFREELIST)
+    {
+        buf->prev = obj_stack_freelist->items;
+        obj_stack_freelist->items = buf;
+        obj_stack_freelist->numfree++;
+    }
+    else {
+        PyMem_RawFree(buf);
+    }
+}
+
+void
+_PyObjectStack_Clear(_PyObjectStack *queue)
+{
+    while (queue->head != NULL) {
+        _PyObjectStackChunk *buf = queue->head;
+        buf->n = 0;
+        queue->head = buf->prev;
+        _PyObjectStackChunk_Free(buf);
+    }
+}
+
+void
+_PyObjectStack_Merge(_PyObjectStack *dst, _PyObjectStack *src)
+{
+    if (src->head == NULL) {
+        return;
+    }
+
+    if (dst->head != NULL) {
+        // First, append dst to the bottom of src
+        _PyObjectStackChunk *last = src->head;
+        while (last->prev != NULL) {
+            last = last->prev;
+        }
+        last->prev = dst->head;
+    }
+
+    // Now that src has all the chunks, set dst to src
+    dst->head = src->head;
+    src->head = NULL;
+}
+
+void
+_PyObjectStackChunk_ClearFreeList(struct _Py_object_freelists *freelists, int is_finalization)
+{
+    if (!is_finalization) {
+        // Ignore requests to clear the free list during GC. We use object
+        // stacks during GC, so emptying the free-list is counterproductive.
+        return;
+    }
+
+    struct _Py_object_stack_freelist *freelist = &freelists->object_stacks;
+    while (freelist->numfree > 0) {
+        _PyObjectStackChunk *buf = freelist->items;
+        freelist->items = buf->prev;
+        freelist->numfree--;
+        PyMem_RawFree(buf);
+    }
+    freelist->numfree = -1;
+}