bpo-32030: Add _PyMainInterpreterConfig.pythonhome (#4513)

* Py_Main() now reads the PYTHONHOME environment variable
* Add _Py_GetPythonHomeWithConfig() private function
* Add _PyWarnings_InitWithConfig()
* init_filters() doesn't get the current core configuration from the
  current interpreter or Python thread anymore. Pass explicitly the
  configuration to _PyWarnings_InitWithConfig().
* _Py_InitializeCore() now fails on _PyWarnings_InitWithConfig()
  failure.
* Pass configuration as constant

Include/pylifecycle.h

@@ -12,6 +12,10 @@ PyAPI_FUNC(wchar_t *) Py_GetProgramName(void);
 
 PyAPI_FUNC(void) Py_SetPythonHome(wchar_t *);
 PyAPI_FUNC(wchar_t *) Py_GetPythonHome(void);
+#ifdef Py_BUILD_CORE
+PyAPI_FUNC(wchar_t *) _Py_GetPythonHomeWithConfig(
+    const _PyMainInterpreterConfig *config);
+#endif
 
 #ifndef Py_LIMITED_API
 /* Only used by applications that embed the interpreter and need to
@@ -94,7 +98,8 @@ PyAPI_FUNC(wchar_t *) Py_GetPrefix(void);
 PyAPI_FUNC(wchar_t *) Py_GetExecPrefix(void);
 PyAPI_FUNC(wchar_t *) Py_GetPath(void);
 #ifdef Py_BUILD_CORE
-PyAPI_FUNC(wchar_t *) _Py_GetPathWithConfig(_PyMainInterpreterConfig *config);
+PyAPI_FUNC(wchar_t *) _Py_GetPathWithConfig(
+    const _PyMainInterpreterConfig *config);
 #endif
 PyAPI_FUNC(void)      Py_SetPath(const wchar_t *);
 #ifdef MS_WINDOWS

Include/pystate.h

@@ -61,12 +61,15 @@ typedef struct {
 typedef struct {
     int install_signal_handlers;
     wchar_t *module_search_path_env; /* PYTHONPATH environment variable */
+    wchar_t *pythonhome;    /* PYTHONHOME environment variable,
+                               see also Py_SetPythonHome(). */
 } _PyMainInterpreterConfig;
 
 #define _PyMainInterpreterConfig_INIT \
     (_PyMainInterpreterConfig){\
      .install_signal_handlers = -1, \
-     .module_search_path_env = NULL}
+     .module_search_path_env = NULL, \
+     .pythonhome = NULL}
 
 typedef struct _is {
 

Include/warnings.h

@@ -7,6 +7,9 @@ extern "C" {
 #ifndef Py_LIMITED_API
 PyAPI_FUNC(PyObject*) _PyWarnings_Init(void);
 #endif
+#ifdef Py_BUILD_CORE
+PyAPI_FUNC(PyObject*) _PyWarnings_InitWithConfig(const _PyCoreConfig *config);
+#endif
 
 PyAPI_FUNC(int) PyErr_WarnEx(
     PyObject *category,

Modules/getpath.c

@@ -456,13 +456,13 @@ search_for_exec_prefix(wchar_t *argv0_path, wchar_t *home,
 }
 
 static void
-calculate_path(_PyMainInterpreterConfig *config)
+calculate_path(const _PyMainInterpreterConfig *config)
 {
     extern wchar_t *Py_GetProgramName(void);
 
     static const wchar_t delimiter[2] = {DELIM, '\0'};
     static const wchar_t separator[2] = {SEP, '\0'};
-    wchar_t *home = Py_GetPythonHome();
+    wchar_t *home = _Py_GetPythonHomeWithConfig(config);
     char *_path = getenv("PATH");
     wchar_t *path_buffer = NULL;
     wchar_t *path = NULL;
@@ -858,7 +858,7 @@ Py_SetPath(const wchar_t *path)
 }
 
 wchar_t *
-_Py_GetPathWithConfig(_PyMainInterpreterConfig *config)
+_Py_GetPathWithConfig(const _PyMainInterpreterConfig *config)
 {
     if (!module_search_path) {
         calculate_path(config);

Modules/main.c

@@ -400,7 +400,6 @@ typedef struct {
     _PyInitError err;
     /* PYTHONWARNINGS env var */
     _Py_OptList env_warning_options;
-    /* PYTHONPATH env var */
     int argc;
     wchar_t **argv;
 } _PyMain;
@@ -1368,43 +1367,94 @@ pymain_set_flags_from_env(_PyMain *pymain)
 
 
 static int
-pymain_init_pythonpath(_PyMain *pymain)
+pymain_get_env_var_dup(_PyMain *pymain, wchar_t **dest,
+                       wchar_t *wname, char *name)
 {
     if (Py_IgnoreEnvironmentFlag) {
+        *dest = NULL;
         return 0;
     }
 
 #ifdef MS_WINDOWS
-    wchar_t *path = _wgetenv(L"PYTHONPATH");
-    if (!path || path[0] == '\0') {
+    wchar_t *var = _wgetenv(wname);
+    if (!var || var[0] == '\0') {
+        *dest = NULL;
         return 0;
     }
 
-    wchar_t *path2 = pymain_wstrdup(pymain, path);
-    if (path2 == NULL) {
+    wchar_t *copy = pymain_wstrdup(pymain, var);
+    if (copy == NULL) {
         return -1;
     }
 
-    pymain->config.module_search_path_env = path2;
+    *dest = copy;
 #else
-    char *path = pymain_get_env_var("PYTHONPATH");
-    if (!path) {
+    char *var = getenv(name);
+    if (!var || var[0] == '\0') {
+        *dest = NULL;
         return 0;
     }
 
     size_t len;
-    wchar_t *wpath = Py_DecodeLocale(path, &len);
-    if (!wpath) {
+    wchar_t *wvar = Py_DecodeLocale(var, &len);
+    if (!wvar) {
         if (len == (size_t)-2) {
-            pymain->err = _Py_INIT_ERR("failed to decode PYTHONHOME");
+            /* don't set pymain->err */
+            return -2;
         }
         else {
             pymain->err = INIT_NO_MEMORY();
+            return -1;
+        }
+    }
+    *dest = wvar;
+#endif
+    return 0;
+}
+
+
+static int
+pymain_init_pythonpath(_PyMain *pymain)
+{
+    wchar_t *path;
+    int res = pymain_get_env_var_dup(pymain, &path,
+                                     L"PYTHONPATH", "PYTHONPATH");
+    if (res < 0) {
+        if (res == -2) {
+            pymain->err = _Py_INIT_ERR("failed to decode PYTHONPATH");
         }
         return -1;
     }
-    pymain->config.module_search_path_env = wpath;
-#endif
+    pymain->config.module_search_path_env = path;
+    return 0;
+}
+
+
+static int
+pymain_init_pythonhome(_PyMain *pymain)
+{
+    wchar_t *home;
+
+    home = Py_GetPythonHome();
+    if (home) {
+        /* Py_SetPythonHome() has been called before Py_Main(),
+           use its value */
+        pymain->config.pythonhome = pymain_wstrdup(pymain, home);
+        if (pymain->config.pythonhome == NULL) {
+            return -1;
+        }
+        return 0;
+    }
+
+    int res = pymain_get_env_var_dup(pymain, &home,
+                                     L"PYTHONHOME", "PYTHONHOME");
+    if (res < 0) {
+        if (res == -2) {
+            pymain->err = _Py_INIT_ERR("failed to decode PYTHONHOME");
+        }
+        return -1;
+    }
+    pymain->config.pythonhome = home;
     return 0;
 }
 
@@ -1433,6 +1483,9 @@ pymain_parse_envvars(_PyMain *pymain)
     if (pymain_init_pythonpath(pymain) < 0) {
         return -1;
     }
+    if (pymain_init_pythonhome(pymain) < 0) {
+        return -1;
+    }
 
     /* -X options */
     if (pymain_get_xoption(pymain, L"showrefcount")) {

PC/getpathp.c

@@ -624,12 +624,12 @@ read_pth_file(const wchar_t *path, wchar_t *prefix, int *isolated, int *nosite)
 
 
 static void
-calculate_path(_PyMainInterpreterConfig *config)
+calculate_path(const _PyMainInterpreterConfig *config)
 {
     wchar_t argv0_path[MAXPATHLEN+1];
     wchar_t *buf;
     size_t bufsz;
-    wchar_t *pythonhome = Py_GetPythonHome();
+    wchar_t *pythonhome = _Py_GetPythonHomeWithConfig(config);
     wchar_t *envpath = NULL;
 
     int skiphome, skipdefault;
@@ -899,7 +899,7 @@ Py_SetPath(const wchar_t *path)
 }
 
 wchar_t *
-_Py_GetPathWithConfig(_PyMainInterpreterConfig *config)
+_Py_GetPathWithConfig(const _PyMainInterpreterConfig *config)
 {
     if (!module_search_path) {
         calculate_path(config);

Python/_warnings.c

@@ -1185,10 +1185,9 @@ create_filter(PyObject *category, const char *action)
 }
 
 static PyObject *
-init_filters(void)
+init_filters(const _PyCoreConfig *config)
 {
-    PyInterpreterState *interp = PyThreadState_GET()->interp;
-    int dev_mode = interp->core_config.dev_mode;
+    int dev_mode = config->dev_mode;
 
     Py_ssize_t count = 2;
     if (dev_mode) {
@@ -1264,8 +1263,8 @@ static struct PyModuleDef warningsmodule = {
 };
 
 
-PyMODINIT_FUNC
-_PyWarnings_Init(void)
+PyObject*
+_PyWarnings_InitWithConfig(const _PyCoreConfig *config)
 {
     PyObject *m;
 
@@ -1274,7 +1273,7 @@ _PyWarnings_Init(void)
         return NULL;
 
     if (_PyRuntime.warnings.filters == NULL) {
-        _PyRuntime.warnings.filters = init_filters();
+        _PyRuntime.warnings.filters = init_filters(config);
         if (_PyRuntime.warnings.filters == NULL)
             return NULL;
     }
@@ -1305,3 +1304,12 @@ _PyWarnings_Init(void)
     _PyRuntime.warnings.filters_version = 0;
     return m;
 }
+
+
+PyMODINIT_FUNC
+_PyWarnings_Init(void)
+{
+    PyInterpreterState *interp = PyThreadState_GET()->interp;
+    const _PyCoreConfig *config = &interp->core_config;
+    return _PyWarnings_InitWithConfig(config);
+}

Python/pylifecycle.c

@@ -767,7 +767,9 @@ _Py_InitializeCore(const _PyCoreConfig *config)
     }
 
     /* Initialize _warnings. */
-    _PyWarnings_Init();
+    if (_PyWarnings_InitWithConfig(&interp->core_config) == NULL) {
+        return _Py_INIT_ERR("can't initialize warnings");
+    }
 
     /* This call sets up builtin and frozen import support */
     if (!interp->core_config._disable_importlib) {
@@ -880,7 +882,7 @@ _Py_InitializeMainInterpreter(const _PyMainInterpreterConfig *config)
         return err;
     }
 
-    if (config->install_signal_handlers) {
+    if (interp->config.install_signal_handlers) {
         err = initsigs(); /* Signal handling stuff, including initintr() */
         if (_Py_INIT_FAILED(err)) {
             return err;
@@ -1468,7 +1470,6 @@ Py_GetProgramName(void)
 }
 
 static wchar_t *default_home = NULL;
-static wchar_t env_home[MAXPATHLEN+1];
 
 void
 Py_SetPythonHome(wchar_t *home)
@@ -1476,21 +1477,41 @@ Py_SetPythonHome(wchar_t *home)
     default_home = home;
 }
 
+wchar_t *
+_Py_GetPythonHomeWithConfig(const _PyMainInterpreterConfig *config)
+{
+    /* 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;
+    }
+
+    if (config) {
+        return config->pythonhome;
+    }
+
+    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;
+}
+
 wchar_t *
 Py_GetPythonHome(void)
 {
-    wchar_t *home = default_home;
-    if (home == NULL && !Py_IgnoreEnvironmentFlag) {
-        char* chome = Py_GETENV("PYTHONHOME");
-        if (chome) {
-            size_t size = Py_ARRAY_LENGTH(env_home);
-            size_t r = mbstowcs(env_home, chome, size);
-            if (r != (size_t)-1 && r < size)
-                home = env_home;
-        }
-
-    }
-    return home;
+    return _Py_GetPythonHomeWithConfig(NULL);
 }
 
 /* Add the __main__ module */