bpo-38304: Add PyConfig.struct_size (GH-16451)

Add a new struct_size field to PyPreConfig and PyConfig structures to
allow to modify these structures in the future without breaking the
backward compatibility.

* Replace private _config_version field with public struct_size field
  in PyPreConfig and PyConfig.
* Public PyPreConfig_InitIsolatedConfig() and
  PyPreConfig_InitPythonConfig()
  return type becomes PyStatus, instead of void.
* Internal _PyConfig_InitCompatConfig(),
  _PyPreConfig_InitCompatConfig(), _PyPreConfig_InitFromConfig(),
  _PyPreConfig_InitFromPreConfig() return type becomes PyStatus,
  instead of void.
* Remove _Py_CONFIG_VERSION
* Update the Initialization Configuration documentation.

1 files changed, 10 insertions, 7 deletions

diff --git a/Include/cpython/initconfig.h b/Include/cpython/initconfig.h
index 047f511..d5effb8 100644
--- a/Include/cpython/initconfig.h
+++ b/Include/cpython/initconfig.h
@@ -45,8 +45,10 @@ PyAPI_FUNC(PyStatus) PyWideStringList_Insert(PyWideStringList *list,
 /* --- PyPreConfig ----------------------------------------------- */
 
 typedef struct {
-    int _config_version;  /* Internal configuration version,
-                             used for ABI compatibility */
+    /* Size of the structure in bytes: must be initialized to
+       sizeof(PyPreConfig). Field used for API and ABI compatibility. */
+    size_t struct_size;
+
     int _config_init;     /* _PyConfigInitEnum value */
 
     /* Parse Py_PreInitializeFromBytesArgs() arguments?
@@ -122,15 +124,17 @@ typedef struct {
     int allocator;
 } PyPreConfig;
 
-PyAPI_FUNC(void) PyPreConfig_InitPythonConfig(PyPreConfig *config);
-PyAPI_FUNC(void) PyPreConfig_InitIsolatedConfig(PyPreConfig *config);
+PyAPI_FUNC(PyStatus) PyPreConfig_InitPythonConfig(PyPreConfig *config);
+PyAPI_FUNC(PyStatus) PyPreConfig_InitIsolatedConfig(PyPreConfig *config);
 
 
 /* --- PyConfig ---------------------------------------------- */
 
 typedef struct {
-    int _config_version;  /* Internal configuration version,
-                             used for ABI compatibility */
+    /* Size of the structure in bytes: must be initialized to
+       sizeof(PyConfig). Field used for API and ABI compatibility. */
+    size_t struct_size;
+
     int _config_init;     /* _PyConfigInitEnum value */
 
     int isolated;         /* Isolated mode? see PyPreConfig.isolated */
@@ -403,7 +407,6 @@ typedef struct {
 
     /* If equal to 0, stop Python initialization before the "main" phase */
     int _init_main;
-
 } PyConfig;
 
 PyAPI_FUNC(PyStatus) PyConfig_InitPythonConfig(PyConfig *config);