add bindings for PyImport_AddModuleRef and use it in Python::run_code

pyo3-ffi/src/compat/py_3_13.rs

@@ -37,3 +37,16 @@ compat_function!(
         item
     }
 );
+
+compat_function!(
+    originally_defined_for(Py_3_13);
+
+    #[inline]
+    pub unsafe fn PyImport_AddModuleRef(
+        name: *const std::os::raw::c_char,
+    ) -> *mut crate::PyObject {
+        use crate::{Py_XNewRef, PyImport_AddModule};
+
+        Py_XNewRef(PyImport_AddModule(name))
+    }
+);

pyo3-ffi/src/import.rs

@@ -30,6 +30,9 @@ extern "C" {
     pub fn PyImport_AddModuleObject(name: *mut PyObject) -> *mut PyObject;
     #[cfg_attr(PyPy, link_name = "PyPyImport_AddModule")]
     pub fn PyImport_AddModule(name: *const c_char) -> *mut PyObject;
+    #[cfg(Py_3_13)]
+    #[cfg_attr(PyPy, link_name = "PyPyImport_AddModuleRef")]
+    pub fn PyImport_AddModuleRef(name: *const c_char) -> *mut PyObject;
     #[cfg_attr(PyPy, link_name = "PyPyImport_ImportModule")]
     pub fn PyImport_ImportModule(name: *const c_char) -> *mut PyObject;
     #[cfg_attr(PyPy, link_name = "PyPyImport_ImportModuleNoBlock")]

src/marker.rs

@@ -634,14 +634,15 @@ impl<'py> Python<'py> {
         locals: Option<&Bound<'py, PyDict>>,
     ) -> PyResult<Bound<'py, PyAny>> {
         unsafe {
-            let mptr = ffi::PyImport_AddModule(ffi::c_str!("__main__").as_ptr());
+            let mptr = ffi::compat::PyImport_AddModuleRef(ffi::c_str!("__main__").as_ptr());
             if mptr.is_null() {
                 return Err(PyErr::fetch(self));
             }
 
             let globals = globals
                 .map(|dict| dict.as_ptr())
                 .unwrap_or_else(|| ffi::PyModule_GetDict(mptr));
+            ffi::Py_DECREF(mptr);
             let locals = locals.map(|dict| dict.as_ptr()).unwrap_or(globals);
 
             // If `globals` don't provide `__builtins__`, most of the code will fail if Python