bpo-36301: Add _PyWstrList structure (GH-12343)

Replace messy _Py_wstrlist_xxx() functions with a new clean
_PyWstrList structure and new _PyWstrList_xxx() functions.

Changes:

* Add _PyCoreConfig.use_module_search_paths to decide if
  _PyCoreConfig.module_search_paths should be computed or not, to
  support empty search path list.
* _PyWstrList_Clear() sets length to 0 and items to NULL, whereas
  _Py_wstrlist_clear() only freed memory.
* _PyWstrList_Append() returns an int, whereas _Py_wstrlist_append()
  returned _PyInitError.
* _PyWstrList uses Py_ssize_t for the length, instead of int.
* Replace (int, wchar_t**) with _PyWstrList in:

  * _PyPreConfig
  * _PyCoreConfig
  * _PyPreCmdline
  * _PyCmdline

* Replace "int orig_argv; wchar_t **orig_argv;"
  with "_PyWstrList orig_argv".
* _PyCmdline and _PyPreCmdline now also copy wchar_argv.
* Rename _PyArgv_Decode() to _PyArgv_AsWstrList().
* PySys_SetArgvEx() now pass the fixed (argc, argv) to
  _PyPathConfig_ComputeArgv0() (don't pass negative argc or NULL
  argv).
* _PyOS_GetOpt() uses Py_ssize_t

4 files changed, 46 insertions, 41 deletions

diff --git a/Include/cpython/coreconfig.h b/Include/cpython/coreconfig.h
index 267357676b..bd28c371ce 100644
--- a/Include/cpython/coreconfig.h
+++ b/Include/cpython/coreconfig.h
@@ -46,6 +46,18 @@ typedef struct {
 #define _Py_INIT_FAILED(err) \
     (err.msg != NULL || err.exitcode != -1)
 
+/* --- _PyWstrList ------------------------------------------------ */
+
+typedef struct {
+    /* If length is greater than zero, items must be non-NULL
+       and all items strings must be non-NULL */
+    Py_ssize_t length;
+    wchar_t **items;
+} _PyWstrList;
+
+#define _PyWstrList_INIT (_PyWstrList){.length = 0, .items = NULL}
+
+
 /* --- _PyPreConfig ----------------------------------------------- */
 
 typedef struct {
@@ -162,19 +174,12 @@ typedef struct {
     char *filesystem_encoding;
     char *filesystem_errors;
 
-    wchar_t *pycache_prefix; /* PYTHONPYCACHEPREFIX, -X pycache_prefix=PATH */
-
-    wchar_t *program_name;  /* Program name, see also Py_GetProgramName() */
-    int argc;               /* Number of command line arguments,
-                               -1 means unset */
-    wchar_t **argv;         /* Command line arguments */
-    wchar_t *program;       /* argv[0] or "" */
-
-    int nxoption;           /* Number of -X options */
-    wchar_t **xoptions;     /* -X options */
-
-    int nwarnoption;        /* Number of warnings options */
-    wchar_t **warnoptions;  /* Warnings options */
+    wchar_t *pycache_prefix;  /* PYTHONPYCACHEPREFIX, -X pycache_prefix=PATH */
+    wchar_t *program_name;    /* Program name, see also Py_GetProgramName() */
+    _PyWstrList argv;         /* Command line arguments */
+    wchar_t *program;         /* argv[0] or "" */
+    _PyWstrList xoptions;     /* Command line -X options */
+    _PyWstrList warnoptions;  /* Warnings options */
 
     /* Path configuration inputs */
     wchar_t *module_search_path_env; /* PYTHONPATH environment variable */
@@ -182,9 +187,11 @@ typedef struct {
                                see also Py_SetPythonHome(). */
 
     /* Path configuration outputs */
-    int nmodule_search_path;        /* Number of sys.path paths,
-                                       -1 means unset */
-    wchar_t **module_search_paths;  /* sys.path paths */
+    int use_module_search_paths;  /* If non-zero, use module_search_paths */
+    _PyWstrList module_search_paths;  /* sys.path paths. Computed if
+                                       use_module_search_paths is equal
+                                       to zero. */
+
     wchar_t *executable;    /* sys.executable */
     wchar_t *prefix;        /* sys.prefix */
     wchar_t *base_prefix;   /* sys.base_prefix */
@@ -366,8 +373,7 @@ typedef struct {
         .use_hash_seed = -1, \
         .faulthandler = -1, \
         .tracemalloc = -1, \
-        .argc = -1, \
-        .nmodule_search_path = -1, \
+        .use_module_search_paths = 0, \
         .site_import = -1, \
         .bytes_warning = -1, \
         .inspect = -1, \
diff --git a/Include/internal/pycore_coreconfig.h b/Include/internal/pycore_coreconfig.h
index 153309de4f..8c5a072e56 100644
--- a/Include/internal/pycore_coreconfig.h
+++ b/Include/internal/pycore_coreconfig.h
@@ -8,39 +8,38 @@ extern "C" {
 #  error "this header requires Py_BUILD_CORE or Py_BUILD_CORE_BUILTIN defined"
 #endif
 
-/* --- _Py_wstrlist ----------------------------------------------- */
-
-PyAPI_FUNC(void) _Py_wstrlist_clear(
-    int len,
-    wchar_t **list);
-PyAPI_FUNC(wchar_t**) _Py_wstrlist_copy(
-    int len,
-    wchar_t * const *list);
-PyAPI_FUNC(_PyInitError) _Py_wstrlist_append(
-    int *len,
-    wchar_t ***list,
-    const wchar_t *str);
-PyAPI_FUNC(PyObject*) _Py_wstrlist_as_pylist(
-    int len,
-    wchar_t **list);
+
+/* --- _PyWstrList ------------------------------------------------ */
+
+#ifndef NDEBUG
+PyAPI_FUNC(int) _PyWstrList_CheckConsistency(const _PyWstrList *list);
+#endif
+PyAPI_FUNC(void) _PyWstrList_Clear(_PyWstrList *list);
+PyAPI_FUNC(int) _PyWstrList_Copy(_PyWstrList *list,
+    const _PyWstrList *list2);
+PyAPI_FUNC(int) _PyWstrList_Append(_PyWstrList *list,
+    const wchar_t *item);
+PyAPI_FUNC(PyObject*) _PyWstrList_AsList(const _PyWstrList *list);
+
 
 /* --- _PyArgv ---------------------------------------------------- */
 
-PyAPI_FUNC(_PyInitError) _PyArgv_Decode(const _PyArgv *args,
-    wchar_t*** argv_p);
+PyAPI_FUNC(_PyInitError) _PyArgv_AsWstrList(const _PyArgv *args,
+    _PyWstrList *list);
+
 
 /* --- Py_GetArgcArgv() helpers ----------------------------------- */
 
 PyAPI_FUNC(void) _Py_ClearArgcArgv(void);
 
+
 /* --- _PyPreConfig ----------------------------------------------- */
 
 PyAPI_FUNC(int) _Py_str_to_int(
     const char *str,
     int *result);
 PyAPI_FUNC(const wchar_t*) _Py_get_xoption(
-    int nxoption,
-    wchar_t * const *xoptions,
+    const _PyWstrList *xoptions,
     const wchar_t *name);
 
 PyAPI_FUNC(void) _PyPreConfig_Clear(_PyPreConfig *config);
diff --git a/Include/internal/pycore_getopt.h b/Include/internal/pycore_getopt.h
index 1d30f5bb99..0d1897c75a 100644
--- a/Include/internal/pycore_getopt.h
+++ b/Include/internal/pycore_getopt.h
@@ -6,8 +6,8 @@
 #endif
 
 extern int _PyOS_opterr;
-extern int _PyOS_optind;
-extern wchar_t *_PyOS_optarg;
+extern Py_ssize_t _PyOS_optind;
+extern const wchar_t *_PyOS_optarg;
 
 extern void _PyOS_ResetGetOpt(void);
 
@@ -17,6 +17,6 @@ typedef struct {
     int val;
 } _PyOS_LongOption;
 
-extern int _PyOS_GetOpt(int argc, wchar_t **argv, int *longindex);
+extern int _PyOS_GetOpt(Py_ssize_t argc, wchar_t **argv, int *longindex);
 
 #endif /* !Py_INTERNAL_PYGETOPT_H */
diff --git a/Include/internal/pycore_pathconfig.h b/Include/internal/pycore_pathconfig.h
index fb6b1d78b3..d0938df541 100644
--- a/Include/internal/pycore_pathconfig.h
+++ b/Include/internal/pycore_pathconfig.h
@@ -44,7 +44,7 @@ PyAPI_FUNC(_PyInitError) _PyPathConfig_SetGlobal(
 PyAPI_FUNC(_PyInitError) _PyPathConfig_Calculate_impl(
     _PyPathConfig *config,
     const _PyCoreConfig *core_config);
-PyAPI_FUNC(PyObject*) _PyPathConfig_ComputeArgv0(int argc, wchar_t **argv);
+PyAPI_FUNC(PyObject*) _PyPathConfig_ComputeArgv0(const _PyWstrList *argv);
 PyAPI_FUNC(int) _Py_FindEnvConfigValue(
     FILE *env_file,
     const wchar_t *key,