bpo-35081: Internal headers require Py_BUILD_CORE (GH-10363)
* All internal header files now require Py_BUILD_CORE or
Py_BUILD_CORE_BUILTIN to be defined.
* _json.c is now compiled with Py_BUILD_CORE_BUILTIN to access
pycore_accu.h header.
* Add an example to Modules/Setup to show how to build _json
as a built-in module; it requires non trivial compiler options.
diff --git a/Include/internal/pycore_ceval.h b/Include/internal/pycore_ceval.h
index ddeeb5c..c8c63b1 100644
--- a/Include/internal/pycore_ceval.h
+++ b/Include/internal/pycore_ceval.h
@@ -4,6 +4,10 @@
extern "C" {
#endif
+#if !defined(Py_BUILD_CORE) && !defined(Py_BUILD_CORE_BUILTIN)
+# error "this header requires Py_BUILD_CORE or Py_BUILD_CORE_BUILTIN define"
+#endif
+
#include "pycore_atomic.h"
#include "pythread.h"