bpo-36763: Add _PyCoreConfig_InitPythonConfig() (GH-13388)

Add new functions to get the Python interpreter behavior:

* _PyPreConfig_InitPythonConfig()
* _PyCoreConfig_InitPythonConfig()

Add new functions to get an isolated configuration:

* _PyPreConfig_InitIsolatedConfig()
* _PyCoreConfig_InitIsolatedConfig()

Replace _PyPreConfig_INIT and _PyCoreConfig_INIT with new functions
_PyPreConfig_Init() and _PyCoreConfig_Init().

_PyCoreConfig: set configure_c_stdio and parse_argv to 0 by default
to behave as Python 3.6 in the default configuration.

_PyCoreConfig_Read() no longer sets coerce_c_locale_warn to 1 if it's
equal to 0. coerce_c_locale_warn must now be set to -1 (ex: using
_PyCoreConfig_InitPythonConfig()) to enable C locale coercion
warning.

Add unit tests for _PyCoreConfig_InitPythonConfig()
and _PyCoreConfig_InitIsolatedConfig().

Changes:

* Rename _PyCoreConfig_GetCoreConfig() to _PyPreConfig_GetCoreConfig()
* Fix core_read_precmdline(): handle parse_argv=0
* Fix _Py_PreInitializeFromCoreConfig(): pass coreconfig.argv
  to _Py_PreInitializeFromPyArgv(), except if parse_argv=0

2 files changed, 31 insertions, 8 deletions

diff --git a/Include/cpython/coreconfig.h b/Include/cpython/coreconfig.h
index dca4134..7d561ce 100644
--- a/Include/cpython/coreconfig.h
+++ b/Include/cpython/coreconfig.h
@@ -86,12 +86,18 @@ typedef struct {
 
        If it is equal to 1, LC_CTYPE locale is read to decide it it should be
        coerced or not (ex: PYTHONCOERCECLOCALE=1). Internally, it is set to 2
-       if the LC_CTYPE locale must be coerced. */
+       if the LC_CTYPE locale must be coerced.
+
+       Disable by default (set to 0). Set it to -1 to let Python decides if it
+       should be enabled or not. */
     int coerce_c_locale;
 
     /* Emit a warning if the LC_CTYPE locale is coerced?
 
-       Disabled by default. Set to 1 by PYTHONCOERCECLOCALE=warn. */
+       Set to 1 by PYTHONCOERCECLOCALE=warn.
+
+       Disable by default (set to 0). Set it to -1 to let Python decides if it
+       should be enabled or not. */
     int coerce_c_locale_warn;
 
 #ifdef MS_WINDOWS
@@ -116,7 +122,10 @@ typedef struct {
        Set to 0 by "-X utf8=0" and PYTHONUTF8=0.
 
        If equals to -1, it is set to 1 if the LC_CTYPE locale is "C" or
-       "POSIX", otherwise inherit Py_UTF8Mode value. */
+       "POSIX", otherwise it is set to 0.
+
+       If equals to -2, inherit Py_UTF8Mode value value (which is equal to 0
+       by default). */
     int utf8_mode;
 
     int dev_mode;           /* Development mode. PYTHONDEVMODE, -X dev */
@@ -138,9 +147,14 @@ typedef struct {
         ._config_version = _Py_CONFIG_VERSION, \
         .isolated = -1, \
         .use_environment = -1, \
+        .utf8_mode = -2, \
         .dev_mode = -1, \
         .allocator = PYMEM_ALLOCATOR_NOT_SET}
 
+PyAPI_FUNC(void) _PyPreConfig_Init(_PyPreConfig *config);
+PyAPI_FUNC(void) _PyPreConfig_InitPythonConfig(_PyPreConfig *config);
+PyAPI_FUNC(void) _PyPreConfig_InitIsolateConfig(_PyPreConfig *config);
+
 
 /* --- _PyCoreConfig ---------------------------------------------- */
 
@@ -213,8 +227,8 @@ typedef struct {
 
     /* Command line arguments (sys.argv).
 
-       By default, Python command line arguments are parsed and then stripped
-       from argv. Set parse_argv to 0 to avoid that.
+       Set parse_argv to 1 to parse argv as Python command line arguments
+       and then strip Python arguments from argv.
 
        If argv is empty, an empty string is added to ensure that sys.argv
        always exists and is never empty. */
@@ -442,7 +456,7 @@ typedef struct {
         .faulthandler = -1, \
         .tracemalloc = -1, \
         .use_module_search_paths = 0, \
-        .parse_argv = 1, \
+        .parse_argv = 0, \
         .site_import = -1, \
         .bytes_warning = -1, \
         .inspect = -1, \
@@ -453,7 +467,7 @@ typedef struct {
         .verbose = -1, \
         .quiet = -1, \
         .user_site_directory = -1, \
-        .configure_c_stdio = 1, \
+        .configure_c_stdio = 0, \
         .buffered_stdio = -1, \
         ._install_importlib = 1, \
         .check_hash_pycs_mode = NULL, \
@@ -461,6 +475,10 @@ typedef struct {
         ._init_main = 1}
 /* Note: _PyCoreConfig_INIT sets other fields to 0/NULL */
 
+PyAPI_FUNC(void) _PyCoreConfig_Init(_PyCoreConfig *config);
+PyAPI_FUNC(_PyInitError) _PyCoreConfig_InitPythonConfig(_PyCoreConfig *config);
+PyAPI_FUNC(_PyInitError) _PyCoreConfig_InitIsolateConfig(_PyCoreConfig *config);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/Include/internal/pycore_coreconfig.h b/Include/internal/pycore_coreconfig.h
index ccb7948..e9c6d9f 100644
--- a/Include/internal/pycore_coreconfig.h
+++ b/Include/internal/pycore_coreconfig.h
@@ -88,10 +88,13 @@ PyAPI_FUNC(_PyInitError) _PyPreCmdline_Read(_PyPreCmdline *cmdline,
 
 /* --- _PyPreConfig ----------------------------------------------- */
 
+PyAPI_FUNC(void) _PyPreConfig_Init(_PyPreConfig *config);
+PyAPI_FUNC(void) _PyPreConfig_InitPythonConfig(_PyPreConfig *config);
+PyAPI_FUNC(void) _PyPreConfig_InitIsolatedConfig(_PyPreConfig *config);
 PyAPI_FUNC(int) _PyPreConfig_Copy(_PyPreConfig *config,
     const _PyPreConfig *config2);
 PyAPI_FUNC(PyObject*) _PyPreConfig_AsDict(const _PyPreConfig *config);
-PyAPI_FUNC(void) _PyCoreConfig_GetCoreConfig(_PyPreConfig *config,
+PyAPI_FUNC(void) _PyPreConfig_GetCoreConfig(_PyPreConfig *config,
     const _PyCoreConfig *core_config);
 PyAPI_FUNC(_PyInitError) _PyPreConfig_Read(_PyPreConfig *config,
     const _PyArgv *args);
@@ -101,6 +104,8 @@ PyAPI_FUNC(_PyInitError) _PyPreConfig_Write(const _PyPreConfig *config);
 /* --- _PyCoreConfig ---------------------------------------------- */
 
 PyAPI_FUNC(void) _PyCoreConfig_Clear(_PyCoreConfig *);
+PyAPI_FUNC(_PyInitError) _PyCoreConfig_InitPythonConfig(_PyCoreConfig *config);
+PyAPI_FUNC(_PyInitError) _PyCoreConfig_InitIsolatedConfig(_PyCoreConfig *config);
 PyAPI_FUNC(_PyInitError) _PyCoreConfig_Copy(
     _PyCoreConfig *config,
     const _PyCoreConfig *config2);