bpo-32030: _PyPathConfig_Init() sets home and program_name (#4673)

_PyPathConfig_Init() now also initialize home and program_name:

* Rename existing _PyPathConfig_Init() to _PyPathConfig_Calculate().
  Add a new _PyPathConfig_Init() function in pathconfig.c which
  handles the _Py_path_config variable and call
  _PyPathConfig_Calculate().
* Add home and program_name fields to _PyPathConfig.home
* _PyPathConfig_Init() now initialize home and program_name
  from main_config
* Py_SetProgramName(), Py_SetPythonHome() and Py_GetPythonHome() now
  calls Py_FatalError() on failure, instead of silently ignoring
  failures.
* config_init_home() now gets directly _Py_path_config.home to only
  get the value set by Py_SetPythonHome(), or NULL if
  Py_SetPythonHome() was not called.
* config_get_program_name() now gets directly
  _Py_path_config.program_name to only get the value set by
  Py_SetProgramName(), or NULL if Py_SetProgramName() was not called.
* pymain_init_python() doesn't call Py_SetProgramName() anymore,
  _PyPathConfig_Init() now always sets the program name
* Call _PyMainInterpreterConfig_Read() in
  pymain_parse_cmdline_envvars_impl() to control the memory allocator
* C API documentation: it's no more safe to call Py_GetProgramName()
  before Py_Initialize().

Doc/c-api/init.rst

@@ -40,7 +40,6 @@ The following functions can be safely called before Python is initialized:
   * :c:func:`Py_GetCompiler`
   * :c:func:`Py_GetCopyright`
   * :c:func:`Py_GetPlatform`
-  * :c:func:`Py_GetProgramName`
   * :c:func:`Py_GetVersion`
 
 * Utilities:
@@ -59,8 +58,8 @@ The following functions can be safely called before Python is initialized:
    The following functions **should not be called** before
    :c:func:`Py_Initialize`: :c:func:`Py_EncodeLocale`, :c:func:`Py_GetPath`,
    :c:func:`Py_GetPrefix`, :c:func:`Py_GetExecPrefix`,
-   :c:func:`Py_GetProgramFullPath`, :c:func:`Py_GetPythonHome` and
-   :c:func:`PyEval_InitThreads`.
+   :c:func:`Py_GetProgramFullPath`, :c:func:`Py_GetPythonHome`,
+   :c:func:`Py_GetProgramName` and :c:func:`PyEval_InitThreads`.
 
 
 .. _global-conf-vars:

Include/internal/pystate.h

@@ -48,12 +48,35 @@ typedef struct {
 #endif
     /* Set by Py_SetPath(), or computed by _PyPathConfig_Init() */
     wchar_t *module_search_path;
+    /* Python program name */
+    wchar_t *program_name;
+    /* Set by Py_SetPythonHome() or PYTHONHOME environment variable */
+    wchar_t *home;
 } _PyPathConfig;
 
-#define _PyPathConfig_INIT {.module_search_path = NULL}
+#ifdef MS_WINDOWS
+#define _PyPathConfig_INIT \
+    {.program_full_path = NULL, \
+     .prefix = NULL, \
+     .dll_path = NULL, \
+     .module_search_path = NULL, \
+     .program_name = NULL, \
+     .home = NULL}
+#else
+#define _PyPathConfig_INIT \
+    {.program_full_path = NULL, \
+     .prefix = NULL, \
+     .exec_prefix = NULL, \
+     .module_search_path = NULL, \
+     .program_name = NULL, \
+     .home = NULL}
+#endif
 
 PyAPI_DATA(_PyPathConfig) _Py_path_config;
 
+PyAPI_FUNC(_PyInitError) _PyPathConfig_Calculate(
+    _PyPathConfig *config,
+    const _PyMainInterpreterConfig *main_config);
 PyAPI_FUNC(void) _PyPathConfig_Clear(_PyPathConfig *config);
 
 

Include/pystate.h

@@ -72,7 +72,8 @@ typedef struct {
     (_PyMainInterpreterConfig){\
      .install_signal_handlers = -1, \
      .module_search_path_env = NULL, \
-     .home = NULL}
+     .home = NULL, \
+     .program_name = NULL}
 
 typedef struct _is {
 

Modules/getpath.c

@@ -1008,16 +1008,10 @@ calculate_path_impl(const _PyMainInterpreterConfig *main_config,
 }
 
 
-/* Initialize paths for Py_GetPath(), Py_GetPrefix(), Py_GetExecPrefix()
-   and Py_GetProgramFullPath() */
 _PyInitError
-_PyPathConfig_Init(const _PyMainInterpreterConfig *main_config)
+_PyPathConfig_Calculate(_PyPathConfig *config,
+                        const _PyMainInterpreterConfig *main_config)
 {
-    if (_Py_path_config.module_search_path) {
-        /* Already initialized */
-        return _Py_INIT_OK();
-    }
-
     PyCalculatePath calculate;
     memset(&calculate, 0, sizeof(calculate));
 
@@ -1026,16 +1020,11 @@ _PyPathConfig_Init(const _PyMainInterpreterConfig *main_config)
         goto done;
     }
 
-    _PyPathConfig new_path_config;
-    memset(&new_path_config, 0, sizeof(new_path_config));
-
-    err = calculate_path_impl(main_config, &calculate, &new_path_config);
+    err = calculate_path_impl(main_config, &calculate, config);
     if (_Py_INIT_FAILED(err)) {
-        _PyPathConfig_Clear(&new_path_config);
         goto done;
     }
 
-    _Py_path_config = new_path_config;
     err = _Py_INIT_OK();
 
 done:

Modules/main.c

@@ -876,6 +876,16 @@ static _PyInitError
 config_get_program_name(_PyMainInterpreterConfig *config)
 {
     assert(config->program_name == NULL);
+
+    /* If Py_SetProgramName() was called, use its value */
+    wchar_t *program_name = _Py_path_config.program_name;
+    if (program_name != NULL) {
+        config->program_name = _PyMem_RawWcsdup(program_name);
+        if (config->program_name == NULL) {
+            return _Py_INIT_NO_MEMORY();
+        }
+    }
+
 #ifdef __APPLE__
     char *p;
     /* On MacOS X, when the Python interpreter is embedded in an
@@ -914,6 +924,7 @@ config_get_program_name(_PyMainInterpreterConfig *config)
     }
 #endif   /* WITH_NEXT_FRAMEWORK */
 #endif   /* __APPLE__ */
+
     return _Py_INIT_OK();
 }
 
@@ -948,13 +959,6 @@ pymain_init_main_interpreter(_PyMain *pymain)
 {
     _PyInitError err;
 
-    /* TODO: Print any exceptions raised by these operations */
-    err = _PyMainInterpreterConfig_Read(&pymain->config);
-    if (_Py_INIT_FAILED(err)) {
-        pymain->err = err;
-        return -1;
-    }
-
     err = _Py_InitializeMainInterpreter(&pymain->config);
     if (_Py_INIT_FAILED(err)) {
         pymain->err = err;
@@ -1412,14 +1416,13 @@ config_init_pythonpath(_PyMainInterpreterConfig *config)
 
 
 static _PyInitError
-config_init_pythonhome(_PyMainInterpreterConfig *config)
+config_init_home(_PyMainInterpreterConfig *config)
 {
     wchar_t *home;
 
-    home = Py_GetPythonHome();
+    /* If Py_SetPythonHome() was called, use its value */
+    home = _Py_path_config.home;
     if (home) {
-        /* Py_SetPythonHome() has been called before Py_Main(),
-           use its value */
         config->home = _PyMem_RawWcsdup(home);
         if (config->home == NULL) {
             return _Py_INIT_NO_MEMORY();
@@ -1439,7 +1442,7 @@ config_init_pythonhome(_PyMainInterpreterConfig *config)
 _PyInitError
 _PyMainInterpreterConfig_ReadEnv(_PyMainInterpreterConfig *config)
 {
-    _PyInitError err = config_init_pythonhome(config);
+    _PyInitError err = config_init_home(config);
     if (_Py_INIT_FAILED(err)) {
         return err;
     }
@@ -1543,6 +1546,12 @@ pymain_parse_cmdline_envvars_impl(_PyMain *pymain)
         return -1;
     }
 
+    _PyInitError err = _PyMainInterpreterConfig_Read(&pymain->config);
+    if (_Py_INIT_FAILED(err)) {
+        pymain->err = err;
+        return -1;
+    }
+
     return 0;
 }
 
@@ -1566,11 +1575,6 @@ pymain_init_python(_PyMain *pymain)
 {
     pymain_init_stdio(pymain);
 
-    Py_SetProgramName(pymain->config.program_name);
-    /* Don't free program_name here: the argument to Py_SetProgramName
-       must remain valid until Py_FinalizeEx is called. The string is freed
-       by pymain_free(). */
-
     pymain->err = _Py_InitializeCore(&pymain->core_config);
     if (_Py_INIT_FAILED(pymain->err)) {
         return -1;

PC/getpathp.c

@@ -1058,38 +1058,23 @@ calculate_free(PyCalculatePath *calculate)
 }
 
 
-/* Initialize paths for Py_GetPath(), Py_GetPrefix(), Py_GetExecPrefix()
-   and Py_GetProgramFullPath() */
 _PyInitError
-_PyPathConfig_Init(const _PyMainInterpreterConfig *main_config)
+_PyPathConfig_Calculate(_PyPathConfig *config,
+                        const _PyMainInterpreterConfig *main_config)
 {
-    if (_Py_path_config.module_search_path) {
-        /* Already initialized */
-        return _Py_INIT_OK();
-    }
-
-    _PyInitError err;
-
     PyCalculatePath calculate;
     memset(&calculate, 0, sizeof(calculate));
 
     calculate_init(&calculate, main_config);
 
-    _PyPathConfig new_path_config;
-    memset(&new_path_config, 0, sizeof(new_path_config));
-
-    err = calculate_path_impl(main_config, &calculate, &new_path_config);
+    _PyInitError err = calculate_path_impl(main_config, &calculate, config);
     if (_Py_INIT_FAILED(err)) {
         goto done;
     }
 
-    _Py_path_config = new_path_config;
     err = _Py_INIT_OK();
 
 done:
-    if (_Py_INIT_FAILED(err)) {
-        _PyPathConfig_Clear(&new_path_config);
-    }
     calculate_free(&calculate);
     return err;
 }

Python/pathconfig.c

@@ -10,17 +10,17 @@ extern "C" {
 
 
 _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)
 {
+    /* _PyMem_SetDefaultAllocator() is needed to get a known memory allocator,
+       since Py_SetPath(), Py_SetPythonHome() and Py_SetProgramName() can be
+       called before Py_Initialize() which can changes the memory allocator. */
+    PyMemAllocatorEx old_alloc;
+    _PyMem_SetDefaultAllocator(PYMEM_DOMAIN_RAW, &old_alloc);
+
 #define CLEAR(ATTR) \
     do { \
         PyMem_RawFree(ATTR); \
@@ -35,57 +35,64 @@ _PyPathConfig_Clear(_PyPathConfig *config)
     CLEAR(config->exec_prefix);
 #endif
     CLEAR(config->module_search_path);
+    CLEAR(config->home);
+    CLEAR(config->program_name);
 #undef CLEAR
-}
 
-
-void
-Py_SetProgramName(wchar_t *pn)
-{
-    if (pn && *pn)
-        progname = pn;
+    PyMem_SetAllocator(PYMEM_DOMAIN_RAW, &old_alloc);
 }
 
 
-wchar_t *
-Py_GetProgramName(void)
+/* Initialize paths for Py_GetPath(), Py_GetPrefix(), Py_GetExecPrefix()
+   and Py_GetProgramFullPath() */
+_PyInitError
+_PyPathConfig_Init(const _PyMainInterpreterConfig *main_config)
 {
-    return progname;
-}
-
-
-void
-Py_SetPythonHome(wchar_t *home)
-{
-    default_home = home;
-}
+    if (_Py_path_config.module_search_path) {
+        /* Already initialized */
+        return _Py_INIT_OK();
+    }
 
+    _PyInitError err;
+    _PyPathConfig new_config = _PyPathConfig_INIT;
 
-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];
+    PyMemAllocatorEx old_alloc;
+    _PyMem_SetDefaultAllocator(PYMEM_DOMAIN_RAW, &old_alloc);
 
-    if (default_home) {
-        return default_home;
+    /* Calculate program_full_path, prefix, exec_prefix (Unix)
+       or dll_path (Windows), and module_search_path */
+    err = _PyPathConfig_Calculate(&new_config, main_config);
+    if (_Py_INIT_FAILED(err)) {
+        _PyPathConfig_Clear(&new_config);
+        goto done;
     }
 
-    char *home = Py_GETENV("PYTHONHOME");
-    if (!home) {
-        return NULL;
+    /* Copy home and program_name from main_config */
+    if (main_config->home != NULL) {
+        new_config.home = _PyMem_RawWcsdup(main_config->home);
+        if (new_config.home == NULL) {
+            err = _Py_INIT_NO_MEMORY();
+            goto done;
+        }
+    }
+    else {
+        new_config.home = 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;
+    new_config.program_name = _PyMem_RawWcsdup(main_config->program_name);
+    if (new_config.program_name == NULL) {
+        err = _Py_INIT_NO_MEMORY();
+        goto done;
     }
 
-    return buffer;
+    _PyPathConfig_Clear(&_Py_path_config);
+    _Py_path_config = new_config;
+
+    err = _Py_INIT_OK();
+
+done:
+    PyMem_SetAllocator(PYMEM_DOMAIN_RAW, &old_alloc);
+    return err;
 }
 
 
@@ -134,6 +141,9 @@ Py_SetPath(const wchar_t *path)
         return;
     }
 
+    PyMemAllocatorEx old_alloc;
+    _PyMem_SetDefaultAllocator(PYMEM_DOMAIN_RAW, &old_alloc);
+
     _PyPathConfig new_config;
     new_config.program_full_path = _PyMem_RawWcsdup(Py_GetProgramName());
     new_config.prefix = _PyMem_RawWcsdup(L"");
@@ -144,8 +154,58 @@ Py_SetPath(const wchar_t *path)
 #endif
     new_config.module_search_path = _PyMem_RawWcsdup(path);
 
+    /* steal the home and program_name values (to leave them unchanged) */
+    new_config.home = _Py_path_config.home;
+    _Py_path_config.home = NULL;
+    new_config.program_name = _Py_path_config.program_name;
+    _Py_path_config.program_name = NULL;
+
     _PyPathConfig_Clear(&_Py_path_config);
     _Py_path_config = new_config;
+
+    PyMem_SetAllocator(PYMEM_DOMAIN_RAW, &old_alloc);
+}
+
+
+void
+Py_SetPythonHome(wchar_t *home)
+{
+    if (home == NULL) {
+        return;
+    }
+
+    PyMemAllocatorEx old_alloc;
+    _PyMem_SetDefaultAllocator(PYMEM_DOMAIN_RAW, &old_alloc);
+
+    PyMem_RawFree(_Py_path_config.home);
+    _Py_path_config.home = _PyMem_RawWcsdup(home);
+
+    PyMem_SetAllocator(PYMEM_DOMAIN_RAW, &old_alloc);
+
+    if (_Py_path_config.home == NULL) {
+        Py_FatalError("Py_SetPythonHome() failed: out of memory");
+    }
+}
+
+
+void
+Py_SetProgramName(wchar_t *program_name)
+{
+    if (program_name == NULL || program_name[0] == L'\0') {
+        return;
+    }
+
+    PyMemAllocatorEx old_alloc;
+    _PyMem_SetDefaultAllocator(PYMEM_DOMAIN_RAW, &old_alloc);
+
+    PyMem_RawFree(_Py_path_config.program_name);
+    _Py_path_config.program_name = _PyMem_RawWcsdup(program_name);
+
+    PyMem_SetAllocator(PYMEM_DOMAIN_RAW, &old_alloc);
+
+    if (_Py_path_config.program_name == NULL) {
+        Py_FatalError("Py_SetProgramName() failed: out of memory");
+    }
 }
 
 
@@ -184,6 +244,23 @@ Py_GetProgramFullPath(void)
     return _Py_path_config.program_full_path;
 }
 
+
+wchar_t*
+Py_GetPythonHome(void)
+{
+    pathconfig_global_init();
+    return _Py_path_config.home;
+}
+
+
+wchar_t *
+Py_GetProgramName(void)
+{
+    pathconfig_global_init();
+    return _Py_path_config.program_name;
+}
+
+
 #ifdef __cplusplus
 }
 #endif

Python/pylifecycle.c

@@ -804,7 +804,12 @@ _PyMainInterpreterConfig_Read(_PyMainInterpreterConfig *config)
     }
 
     if (config->program_name == NULL) {
-        config->program_name = _PyMem_RawWcsdup(Py_GetProgramName());
+#ifdef MS_WINDOWS
+        const wchar_t *program_name = L"python";
+#else
+        const wchar_t *program_name = L"python3";
+#endif
+        config->program_name = _PyMem_RawWcsdup(program_name);
         if (config->program_name == NULL) {
             return _Py_INIT_NO_MEMORY();
         }