bpo-43244: Remove the pyarena.h header (GH-25007)

Remove the pyarena.h header file with functions:

* PyArena_New()
* PyArena_Free()
* PyArena_Malloc()
* PyArena_AddPyObject()

These functions were undocumented, excluded from the limited C API,
and were only used internally by the compiler.

Add pycore_pyarena.h header. Rename functions:

* PyArena_New() => _PyArena_New()
* PyArena_Free() => _PyArena_Free()
* PyArena_Malloc() => _PyArena_Malloc()
* PyArena_AddPyObject() => _PyArena_AddPyObject()

5 files changed, 71 insertions, 69 deletions

diff --git a/Include/Python.h b/Include/Python.h
index c87a7dd..1df2fd5 100644
--- a/Include/Python.h
+++ b/Include/Python.h
@@ -137,7 +137,6 @@
 #include "pystate.h"
 #include "context.h"
 
-#include "cpython/pyarena.h"
 #include "modsupport.h"
 #include "compile.h"
 #include "pythonrun.h"
diff --git a/Include/cpython/pyarena.h b/Include/cpython/pyarena.h
deleted file mode 100644
index db3ad01..0000000
--- a/Include/cpython/pyarena.h
+++ /dev/null
@@ -1,64 +0,0 @@
-/* An arena-like memory interface for the compiler.
- */
-
-#ifndef Py_LIMITED_API
-#ifndef Py_PYARENA_H
-#define Py_PYARENA_H
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
-  typedef struct _arena PyArena;
-
-  /* PyArena_New() and PyArena_Free() create a new arena and free it,
-     respectively.  Once an arena has been created, it can be used
-     to allocate memory via PyArena_Malloc().  Pointers to PyObject can
-     also be registered with the arena via PyArena_AddPyObject(), and the
-     arena will ensure that the PyObjects stay alive at least until
-     PyArena_Free() is called.  When an arena is freed, all the memory it
-     allocated is freed, the arena releases internal references to registered
-     PyObject*, and none of its pointers are valid.
-     XXX (tim) What does "none of its pointers are valid" mean?  Does it
-     XXX mean that pointers previously obtained via PyArena_Malloc() are
-     XXX no longer valid?  (That's clearly true, but not sure that's what
-     XXX the text is trying to say.)
-
-     PyArena_New() returns an arena pointer.  On error, it
-     returns a negative number and sets an exception.
-     XXX (tim):  Not true.  On error, PyArena_New() actually returns NULL,
-     XXX and looks like it may or may not set an exception (e.g., if the
-     XXX internal PyList_New(0) returns NULL, PyArena_New() passes that on
-     XXX and an exception is set; OTOH, if the internal
-     XXX block_new(DEFAULT_BLOCK_SIZE) returns NULL, that's passed on but
-     XXX an exception is not set in that case).
-  */
-  PyAPI_FUNC(PyArena *) PyArena_New(void);
-  PyAPI_FUNC(void) PyArena_Free(PyArena *);
-
-  /* Mostly like malloc(), return the address of a block of memory spanning
-   * `size` bytes, or return NULL (without setting an exception) if enough
-   * new memory can't be obtained.  Unlike malloc(0), PyArena_Malloc() with
-   * size=0 does not guarantee to return a unique pointer (the pointer
-   * returned may equal one or more other pointers obtained from
-   * PyArena_Malloc()).
-   * Note that pointers obtained via PyArena_Malloc() must never be passed to
-   * the system free() or realloc(), or to any of Python's similar memory-
-   * management functions.  PyArena_Malloc()-obtained pointers remain valid
-   * until PyArena_Free(ar) is called, at which point all pointers obtained
-   * from the arena `ar` become invalid simultaneously.
-   */
-  PyAPI_FUNC(void *) PyArena_Malloc(PyArena *, size_t size);
-
-  /* This routine isn't a proper arena allocation routine.  It takes
-   * a PyObject* and records it so that it can be DECREFed when the
-   * arena is freed.
-   */
-  PyAPI_FUNC(int) PyArena_AddPyObject(PyArena *, PyObject *);
-
-#ifdef __cplusplus
-}
-#endif
-
-#endif /* !Py_PYARENA_H */
-#endif /* Py_LIMITED_API */
diff --git a/Include/internal/pycore_asdl.h b/Include/internal/pycore_asdl.h
index 4df0e34..c0b07c3 100644
--- a/Include/internal/pycore_asdl.h
+++ b/Include/internal/pycore_asdl.h
@@ -8,6 +8,8 @@ extern "C" {
 #  error "this header requires Py_BUILD_CORE define"
 #endif
 
+#include "pycore_pyarena.h"       // _PyArena_Malloc()
+
 typedef PyObject * identifier;
 typedef PyObject * string;
 typedef PyObject * object;
@@ -65,7 +67,7 @@ asdl_ ## NAME ## _seq *_Py_asdl_ ## NAME ## _seq_new(Py_ssize_t size, PyArena *a
         return NULL; \
     } \
     n += sizeof(asdl_ ## NAME ## _seq); \
-    seq = (asdl_ ## NAME ## _seq *)PyArena_Malloc(arena, n); \
+    seq = (asdl_ ## NAME ## _seq *)_PyArena_Malloc(arena, n); \
     if (!seq) { \
         PyErr_NoMemory(); \
         return NULL; \
diff --git a/Include/internal/pycore_compile.h b/Include/internal/pycore_compile.h
index f6caec3..e8859bb 100644
--- a/Include/internal/pycore_compile.h
+++ b/Include/internal/pycore_compile.h
@@ -8,7 +8,8 @@ extern "C" {
 #  error "this header requires Py_BUILD_CORE define"
 #endif
 
-struct _mod;   // Type defined in pycore_ast.h
+struct _arena;   // Type defined in pycore_pyarena.h
+struct _mod;     // Type defined in pycore_ast.h
 
 // Export the symbol for test_peg_generator (built as a library)
 PyAPI_FUNC(PyCodeObject*) _PyAST_Compile(
@@ -16,7 +17,7 @@ PyAPI_FUNC(PyCodeObject*) _PyAST_Compile(
     PyObject *filename,
     PyCompilerFlags *flags,
     int optimize,
-    PyArena *arena);
+    struct _arena *arena);
 extern PyFutureFeatures* _PyFuture_FromAST(
     struct _mod * mod,
     PyObject *filename
@@ -31,7 +32,7 @@ typedef struct {
 
 extern int _PyAST_Optimize(
     struct _mod *,
-    PyArena *arena,
+    struct _arena *arena,
     _PyASTOptimizeState *state);
 
 #ifdef __cplusplus
diff --git a/Include/internal/pycore_pyarena.h b/Include/internal/pycore_pyarena.h
new file mode 100644
index 0000000..d78972a
--- /dev/null
+++ b/Include/internal/pycore_pyarena.h
@@ -0,0 +1,64 @@
+/* An arena-like memory interface for the compiler.
+ */
+
+#ifndef Py_INTERNAL_PYARENA_H
+#define Py_INTERNAL_PYARENA_H
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#ifndef Py_BUILD_CORE
+#  error "this header requires Py_BUILD_CORE define"
+#endif
+
+typedef struct _arena PyArena;
+
+/* _PyArena_New() and _PyArena_Free() create a new arena and free it,
+   respectively.  Once an arena has been created, it can be used
+   to allocate memory via _PyArena_Malloc().  Pointers to PyObject can
+   also be registered with the arena via _PyArena_AddPyObject(), and the
+   arena will ensure that the PyObjects stay alive at least until
+   _PyArena_Free() is called.  When an arena is freed, all the memory it
+   allocated is freed, the arena releases internal references to registered
+   PyObject*, and none of its pointers are valid.
+   XXX (tim) What does "none of its pointers are valid" mean?  Does it
+   XXX mean that pointers previously obtained via _PyArena_Malloc() are
+   XXX no longer valid?  (That's clearly true, but not sure that's what
+   XXX the text is trying to say.)
+
+   _PyArena_New() returns an arena pointer.  On error, it
+   returns a negative number and sets an exception.
+   XXX (tim):  Not true.  On error, _PyArena_New() actually returns NULL,
+   XXX and looks like it may or may not set an exception (e.g., if the
+   XXX internal PyList_New(0) returns NULL, _PyArena_New() passes that on
+   XXX and an exception is set; OTOH, if the internal
+   XXX block_new(DEFAULT_BLOCK_SIZE) returns NULL, that's passed on but
+   XXX an exception is not set in that case).
+*/
+PyAPI_FUNC(PyArena*) _PyArena_New(void);
+PyAPI_FUNC(void) _PyArena_Free(PyArena *);
+
+/* Mostly like malloc(), return the address of a block of memory spanning
+ * `size` bytes, or return NULL (without setting an exception) if enough
+ * new memory can't be obtained.  Unlike malloc(0), _PyArena_Malloc() with
+ * size=0 does not guarantee to return a unique pointer (the pointer
+ * returned may equal one or more other pointers obtained from
+ * _PyArena_Malloc()).
+ * Note that pointers obtained via _PyArena_Malloc() must never be passed to
+ * the system free() or realloc(), or to any of Python's similar memory-
+ * management functions.  _PyArena_Malloc()-obtained pointers remain valid
+ * until _PyArena_Free(ar) is called, at which point all pointers obtained
+ * from the arena `ar` become invalid simultaneously.
+ */
+PyAPI_FUNC(void*) _PyArena_Malloc(PyArena *, size_t size);
+
+/* This routine isn't a proper arena allocation routine.  It takes
+ * a PyObject* and records it so that it can be DECREFed when the
+ * arena is freed.
+ */
+PyAPI_FUNC(int) _PyArena_AddPyObject(PyArena *, PyObject *);
+
+#ifdef __cplusplus
+}
+#endif
+#endif /* !Py_INTERNAL_PYARENA_H */