BUG: Add object cast to avoid warning with limited API

To be honest, I think we should just delete this from the public API.
But I thought I'll start with this, since at least in
principle that isn't a bug-release thing to backport.

I am not sure setting warnings to errors is wise (at least for Cython and
MSVC).  OTOH, the Cython module currently truly does nothing except
include the headers (it doesn't even use the NumPy `.pyd` yet).

Author: seberg

numpy/_core/include/numpy/dtype_api.h

@@ -449,7 +449,7 @@ typedef PyArray_DTypeMeta *(PyArrayDTypeMeta_CommonDType)(
 
 static inline PyArray_DTypeMeta *
 NPY_DT_NewRef(PyArray_DTypeMeta *o) {
-    Py_INCREF(o);
+    Py_INCREF((PyObject *)o);
     return o;
 }
 

numpy/_core/tests/examples/limited_api/limited_api_latest.c

@@ -0,0 +1,19 @@
+#if Py_LIMITED_API != PY_VERSION_HEX & 0xffff0000
+    # error "Py_LIMITED_API not defined to Python major+minor version"
+#endif
+
+#include <Python.h>
+#include <numpy/arrayobject.h>
+#include <numpy/ufuncobject.h>
+
+static PyModuleDef moduledef = {
+    .m_base = PyModuleDef_HEAD_INIT,
+    .m_name = "limited_api_latest"
+};
+
+PyMODINIT_FUNC PyInit_limited_api_latest(void)
+{
+    import_array();
+    import_umath();
+    return PyModule_Create(&moduledef);
+}

numpy/_core/tests/examples/limited_api/meson.build

@@ -34,6 +34,16 @@ py.extension_module(
     limited_api: '3.6',
 )
 
+py.extension_module(
+    'limited_api_latest',
+    'limited_api_latest.c',
+    c_args: [
+      '-DNPY_NO_DEPRECATED_API=NPY_1_21_API_VERSION',
+    ],
+    include_directories: [npy_include_path],
+    limited_api: py.language_version(),
+)
+
 py.extension_module(
     'limited_api2',
     'limited_api2.pyx',

numpy/_core/tests/test_limited_api.py

@@ -47,16 +47,18 @@ def install_temp(tmpdir_factory):
         pytest.skip("No usable 'meson' found")
     if sys.platform == "win32":
         subprocess.check_call(["meson", "setup",
+                               "--werror",
                                "--buildtype=release",
                                "--vsenv", str(srcdir)],
                               cwd=build_dir,
                               )
     else:
-        subprocess.check_call(["meson", "setup", str(srcdir)],
+        subprocess.check_call(["meson", "setup", "--werror", str(srcdir)],
                               cwd=build_dir
                               )
     try:
-        subprocess.check_call(["meson", "compile", "-vv"], cwd=build_dir)
+        subprocess.check_call(
+            ["meson", "compile", "-vv"], cwd=build_dir)
     except subprocess.CalledProcessError as p:
         print(f"{p.stdout=}")
         print(f"{p.stderr=}")
@@ -84,5 +86,6 @@ def test_limited_api(install_temp):
     and building a cython extension with the limited API
     """
 
-    import limited_api1
-    import limited_api2
+    import limited_api1  # Earliest (3.6)
+    import limited_api_latest  # Latest version (current Python)
+    import limited_api2  # cython