Rename variables to _PY_IMPL_NAME and _PY_IMPL_CACHE_TAG

Author: zooba

Misc/NEWS.d/next/Build/2026-01-27-23-39-26.gh-issue-144278.tejFwL.rst

@@ -1,4 +1,5 @@
-Enables patching the ``TAG`` preprocessor definition to override
-:data:`sys.implementation.cache_tag <sys.implementation>` at build time.
-Setting it to ``NULL`` has the effect of completely disabling automatic
-creation and use of ``.pyc`` files.
+Enables defining the ``_PY_IMPL_NAME`` and ``_PY_IMPL_CACHE_TAG`` preprocessor
+definitions to override :data:`sys.implementation` at build time. Definitions
+need to include quotes when setting to a string literal. Setting the cache tag
+to ``NULL`` has the effect of completely disabling automatic creation and use of
+``.pyc`` files.

Python/sysmodule.c

@@ -3568,18 +3568,20 @@ make_version_info(PyThreadState *tstate)
 }
 
 /* sys.implementation values */
-#define NAME "cpython"
-const char *_PySys_ImplName = NAME;
+#ifndef _PY_IMPL_NAME
+#define _PY_IMPL_NAME "cpython"
+#endif
+const char *_PySys_ImplName = _PY_IMPL_NAME;
+#ifndef _PY_IMPL_CACHE_TAG
 #define MAJOR Py_STRINGIFY(PY_MAJOR_VERSION)
 #define MINOR Py_STRINGIFY(PY_MINOR_VERSION)
-#ifndef TAG
-#define TAG NAME "-" MAJOR MINOR
+#define _PY_IMPL_CACHE_TAG NAME "-" MAJOR MINOR
 #endif
-const char *_PySys_ImplCacheTag = TAG;
-#undef NAME
+const char *_PySys_ImplCacheTag = _PY_IMPL_CACHE_TAG;
+#ifndef _PY_IMPL_CACHE_TAG
 #undef MAJOR
 #undef MINOR
-#undef TAG
+#endif
 
 static PyObject *
 make_impl_info(PyObject *version_info)