gh-100146: Steal references from stack when building a list (#100147)

When executing the BUILD_LIST opcode, steal the references from the stack,
in a manner similar to the BUILD_TUPLE opcode.  Implement this by offloading
the logic to a new private API, _PyList_FromArraySteal(), that works similarly
to _PyTuple_FromArraySteal().

This way, instead of performing multiple stack pointer adjustments while the
list is being initialized, the stack is adjusted only once and a fast memory
copy operation is performed in one fell swoop.

1 files changed, 2 insertions, 0 deletions

diff --git a/Include/internal/pycore_list.h b/Include/internal/pycore_list.h
index 628267c..2fcbe12 100644
--- a/Include/internal/pycore_list.h
+++ b/Include/internal/pycore_list.h
@@ -75,6 +75,8 @@ typedef struct {
     PyListObject *it_seq; /* Set to NULL when iterator is exhausted */
 } _PyListIterObject;
 
+extern PyObject *_PyList_FromArraySteal(PyObject *const *src, Py_ssize_t n);
+
 #ifdef __cplusplus
 }
 #endif