gh-108220: Internal header files require Py_BUILD_CORE to be defined (#108221)

* pycore_intrinsics.h does nothing if included twice
  (add #ifndef and #define).
* Update Tools/cases_generator/generate_cases.py to generate the
  Py_BUILD_CORE test.
* _bz2, _lzma, _opcode and zlib extensions now define the
  Py_BUILD_CORE_MODULE macro to use internal headers
  (pycore_code.h, pycore_intrinsics.h and pycore_blocks_output_buffer.h).

Include/internal/pycore_blocks_output_buffer.h

@@ -40,6 +40,10 @@ extern "C" {
 
 #include "Python.h"
 
+#ifndef Py_BUILD_CORE
+#  error "this header requires Py_BUILD_CORE define"
+#endif
+
 typedef struct {
     // List of bytes objects
     PyObject *list;

Include/internal/pycore_code.h

@@ -4,6 +4,10 @@
 extern "C" {
 #endif
 
+#ifndef Py_BUILD_CORE
+#  error "this header requires Py_BUILD_CORE define"
+#endif
+
 #define CODE_MAX_WATCHERS 8
 
 /* PEP 659

Include/internal/pycore_codecs.h

@@ -4,6 +4,10 @@
 extern "C" {
 #endif
 
+#ifndef Py_BUILD_CORE
+#  error "this header requires Py_BUILD_CORE define"
+#endif
+
 extern PyObject* _PyCodec_Lookup(const char *encoding);
 
 /* Text codec specific encoding and decoding API.

Include/internal/pycore_emscripten_signal.h

@@ -3,6 +3,10 @@
 
 #if defined(__EMSCRIPTEN__)
 
+#ifndef Py_BUILD_CORE
+#  error "this header requires Py_BUILD_CORE define"
+#endif
+
 void
 _Py_CheckEmscriptenSignals(void);
 

Include/internal/pycore_fileutils.h

@@ -5,7 +5,7 @@ extern "C" {
 #endif
 
 #ifndef Py_BUILD_CORE
-#  error "Py_BUILD_CORE must be defined to include this header"
+#  error "this header requires Py_BUILD_CORE define"
 #endif
 
 #include <locale.h>   /* struct lconv */

Include/internal/pycore_fileutils_windows.h

@@ -5,7 +5,7 @@ extern "C" {
 #endif
 
 #ifndef Py_BUILD_CORE
-#  error "Py_BUILD_CORE must be defined to include this header"
+#  error "this header requires Py_BUILD_CORE define"
 #endif
 
 #ifdef MS_WINDOWS

Include/internal/pycore_frame.h

@@ -4,6 +4,10 @@
 extern "C" {
 #endif
 
+#ifndef Py_BUILD_CORE
+#  error "this header requires Py_BUILD_CORE define"
+#endif
+
 #include <stdbool.h>
 #include <stddef.h>               // offsetof()
 #include "pycore_code.h"          // STATS

Include/internal/pycore_import.h

@@ -5,6 +5,10 @@
 extern "C" {
 #endif
 
+#ifndef Py_BUILD_CORE
+#  error "this header requires Py_BUILD_CORE define"
+#endif
+
 #include "pycore_hashtable.h"     // _Py_hashtable_t
 #include "pycore_time.h"          // _PyTime_t
 

Include/internal/pycore_instruments.h

@@ -1,7 +1,9 @@
-
 #ifndef Py_INTERNAL_INSTRUMENT_H
 #define Py_INTERNAL_INSTRUMENT_H
 
+#ifndef Py_BUILD_CORE
+#  error "this header requires Py_BUILD_CORE define"
+#endif
 
 #include "pycore_bitutils.h"      // _Py_popcount32
 #include "pycore_frame.h"

Include/internal/pycore_intrinsics.h

@@ -1,3 +1,9 @@
+#ifndef Py_INTERNAL_INTRINSIC_H
+#define Py_INTERNAL_INTRINSIC_H
+
+#ifndef Py_BUILD_CORE
+#  error "this header requires Py_BUILD_CORE define"
+#endif
 
 /* Unary Functions: */
 #define INTRINSIC_1_INVALID                      0
@@ -40,3 +46,5 @@ typedef struct {
 
 extern const intrinsic_func1_info _PyIntrinsics_UnaryFunctions[];
 extern const intrinsic_func2_info _PyIntrinsics_BinaryFunctions[];
+
+#endif  // !Py_INTERNAL_INTRINSIC_H

Include/internal/pycore_opcode_metadata.h

@@ -3,6 +3,10 @@
 //   Python/bytecodes.c
 // Do not edit!
 
+#ifndef Py_BUILD_CORE
+#  error "this header requires Py_BUILD_CORE define"
+#endif
+
 #include <stdbool.h>
 
 

Modules/_bz2module.c

@@ -1,5 +1,9 @@
 /* _bz2 - Low-level Python interface to libbzip2. */
 
+#ifndef Py_BUILD_CORE_BUILTIN
+#  define Py_BUILD_CORE_MODULE 1
+#endif
+
 #include "Python.h"
 
 #include <bzlib.h>

Modules/_lzmamodule.c

@@ -5,6 +5,10 @@
 
 */
 
+#ifndef Py_BUILD_CORE_BUILTIN
+#  define Py_BUILD_CORE_MODULE 1
+#endif
+
 #include "Python.h"
 
 

Modules/_opcode.c

@@ -1,3 +1,7 @@
+#ifndef Py_BUILD_CORE_BUILTIN
+#  define Py_BUILD_CORE_MODULE 1
+#endif
+
 #include "Python.h"
 #include "compile.h"
 #include "opcode.h"

Modules/zlibmodule.c

@@ -3,6 +3,10 @@
 
 /* Windows users:  read Python's PCbuild\readme.txt */
 
+#ifndef Py_BUILD_CORE_BUILTIN
+#  define Py_BUILD_CORE_MODULE 1
+#endif
+
 #include "Python.h"
 
 #include "zlib.h"

Tools/cases_generator/generate_cases.py

@@ -9,6 +9,7 @@
 import os
 import posixpath
 import sys
+import textwrap
 import typing
 from collections.abc import Iterator
 
@@ -403,6 +404,12 @@ def write_metadata(self, metadata_filename: str, pymetadata_filename: str) -> No
 
             self.write_provenance_header()
 
+            self.out.emit("\n" + textwrap.dedent("""
+                #ifndef Py_BUILD_CORE
+                #  error "this header requires Py_BUILD_CORE define"
+                #endif
+            """).strip())
+
             self.out.emit("\n#include <stdbool.h>")
 
             self.write_pseudo_instrs()