bpo-32030: Add Python/pathconfig.c (#4668)

* Factorize code from PC/getpathp.c and Modules/getpath.c to remove
  duplicated code
* rename pathconfig_clear() to _PyPathConfig_Clear()
* Inline _PyPathConfig_Fini() in pymain_impl() and then remove it,
  since it's a oneliner

Python/pathconfig.c

@@ -0,0 +1,189 @@
+/* Path configuration like module_search_path (sys.path) */
+
+#include "Python.h"
+#include "osdefs.h"
+#include "internal/pystate.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+
+_PyPathConfig _Py_path_config = _PyPathConfig_INIT;
+#ifdef MS_WINDOWS
+static wchar_t *progname = L"python";
+#else
+static wchar_t *progname = L"python3";
+#endif
+static wchar_t *default_home = NULL;
+
+
+void
+_PyPathConfig_Clear(_PyPathConfig *config)
+{
+#define CLEAR(ATTR) \
+    do { \
+        PyMem_RawFree(ATTR); \
+        ATTR = NULL; \
+    } while (0)
+
+    CLEAR(config->prefix);
+    CLEAR(config->program_full_path);
+#ifdef MS_WINDOWS
+    CLEAR(config->dll_path);
+#else
+    CLEAR(config->exec_prefix);
+#endif
+    CLEAR(config->module_search_path);
+#undef CLEAR
+}
+
+
+void
+Py_SetProgramName(wchar_t *pn)
+{
+    if (pn && *pn)
+        progname = pn;
+}
+
+
+wchar_t *
+Py_GetProgramName(void)
+{
+    return progname;
+}
+
+
+void
+Py_SetPythonHome(wchar_t *home)
+{
+    default_home = home;
+}
+
+
+wchar_t*
+Py_GetPythonHome(void)
+{
+    /* Use a static buffer to avoid heap memory allocation failure.
+       Py_GetPythonHome() doesn't allow to report error, and the caller
+       doesn't release memory. */
+    static wchar_t buffer[MAXPATHLEN+1];
+
+    if (default_home) {
+        return default_home;
+    }
+
+    char *home = Py_GETENV("PYTHONHOME");
+    if (!home) {
+        return NULL;
+    }
+
+    size_t size = Py_ARRAY_LENGTH(buffer);
+    size_t r = mbstowcs(buffer, home, size);
+    if (r == (size_t)-1 || r >= size) {
+        /* conversion failed or the static buffer is too small */
+        return NULL;
+    }
+
+    return buffer;
+}
+
+
+static void
+pathconfig_global_init(void)
+{
+    if (_Py_path_config.module_search_path) {
+        /* Already initialized */
+        return;
+    }
+
+    _PyInitError err;
+    _PyMainInterpreterConfig config = _PyMainInterpreterConfig_INIT;
+
+    err = _PyMainInterpreterConfig_ReadEnv(&config);
+    if (_Py_INIT_FAILED(err)) {
+        goto error;
+    }
+
+    err = _PyMainInterpreterConfig_Read(&config);
+    if (_Py_INIT_FAILED(err)) {
+        goto error;
+    }
+
+    err = _PyPathConfig_Init(&config);
+    if (_Py_INIT_FAILED(err)) {
+        goto error;
+    }
+
+    _PyMainInterpreterConfig_Clear(&config);
+    return;
+
+error:
+    _PyMainInterpreterConfig_Clear(&config);
+    _Py_FatalInitError(err);
+}
+
+
+/* External interface */
+
+void
+Py_SetPath(const wchar_t *path)
+{
+    if (path == NULL) {
+        _PyPathConfig_Clear(&_Py_path_config);
+        return;
+    }
+
+    _PyPathConfig new_config;
+    new_config.program_full_path = _PyMem_RawWcsdup(Py_GetProgramName());
+    new_config.prefix = _PyMem_RawWcsdup(L"");
+#ifdef MS_WINDOWS
+    new_config.dll_path = _PyMem_RawWcsdup(L"");
+#else
+    new_config.exec_prefix = _PyMem_RawWcsdup(L"");
+#endif
+    new_config.module_search_path = _PyMem_RawWcsdup(path);
+
+    _PyPathConfig_Clear(&_Py_path_config);
+    _Py_path_config = new_config;
+}
+
+
+wchar_t *
+Py_GetPath(void)
+{
+    pathconfig_global_init();
+    return _Py_path_config.module_search_path;
+}
+
+
+wchar_t *
+Py_GetPrefix(void)
+{
+    pathconfig_global_init();
+    return _Py_path_config.prefix;
+}
+
+
+wchar_t *
+Py_GetExecPrefix(void)
+{
+#ifdef MS_WINDOWS
+    return Py_GetPrefix();
+#else
+    pathconfig_global_init();
+    return _Py_path_config.exec_prefix;
+#endif
+}
+
+
+wchar_t *
+Py_GetProgramFullPath(void)
+{
+    pathconfig_global_init();
+    return _Py_path_config.program_full_path;
+}
+
+#ifdef __cplusplus
+}
+#endif

Python/pylifecycle.c

@@ -1489,61 +1489,6 @@ Py_EndInterpreter(PyThreadState *tstate)
     PyInterpreterState_Delete(interp);
 }
 
-#ifdef MS_WINDOWS
-static wchar_t *progname = L"python";
-#else
-static wchar_t *progname = L"python3";
-#endif
-
-void
-Py_SetProgramName(wchar_t *pn)
-{
-    if (pn && *pn)
-        progname = pn;
-}
-
-wchar_t *
-Py_GetProgramName(void)
-{
-    return progname;
-}
-
-static wchar_t *default_home = NULL;
-
-void
-Py_SetPythonHome(wchar_t *home)
-{
-    default_home = home;
-}
-
-
-wchar_t*
-Py_GetPythonHome(void)
-{
-    /* Use a static buffer to avoid heap memory allocation failure.
-       Py_GetPythonHome() doesn't allow to report error, and the caller
-       doesn't release memory. */
-    static wchar_t buffer[MAXPATHLEN+1];
-
-    if (default_home) {
-        return default_home;
-    }
-
-    char *home = Py_GETENV("PYTHONHOME");
-    if (!home) {
-        return NULL;
-    }
-
-    size_t size = Py_ARRAY_LENGTH(buffer);
-    size_t r = mbstowcs(buffer, home, size);
-    if (r == (size_t)-1 || r >= size) {
-        /* conversion failed or the static buffer is too small */
-        return NULL;
-    }
-
-    return buffer;
-}
-
 /* Add the __main__ module */
 
 static _PyInitError