bpo-37369: Fix initialization of sys members when launched via an app container (GH-14428)

sys._base_executable is now always defined on all platforms, and can be overridden through configuration.
Also adds test.support.PythonSymlink to encapsulate platform-specific logic for symlinking sys.executable

3 files changed, 35 insertions, 0 deletions

diff --git a/Python/initconfig.c b/Python/initconfig.c
index 9c4cfbe..786f694 100644
--- a/Python/initconfig.c
+++ b/Python/initconfig.c
@@ -528,6 +528,7 @@ PyConfig_Clear(PyConfig *config)
     config->module_search_paths_set = 0;
 
     CLEAR(config->executable);
+    CLEAR(config->base_executable);
     CLEAR(config->prefix);
     CLEAR(config->base_prefix);
     CLEAR(config->exec_prefix);
@@ -765,6 +766,7 @@ _PyConfig_Copy(PyConfig *config, const PyConfig *config2)
     COPY_ATTR(module_search_paths_set);
 
     COPY_WSTR_ATTR(executable);
+    COPY_WSTR_ATTR(base_executable);
     COPY_WSTR_ATTR(prefix);
     COPY_WSTR_ATTR(base_prefix);
     COPY_WSTR_ATTR(exec_prefix);
@@ -865,6 +867,7 @@ config_as_dict(const PyConfig *config)
     SET_ITEM_WSTR(home);
     SET_ITEM_WSTRLIST(module_search_paths);
     SET_ITEM_WSTR(executable);
+    SET_ITEM_WSTR(base_executable);
     SET_ITEM_WSTR(prefix);
     SET_ITEM_WSTR(base_prefix);
     SET_ITEM_WSTR(exec_prefix);
@@ -2404,6 +2407,7 @@ PyConfig_Read(PyConfig *config)
         assert(config->module_search_paths_set != 0);
         /* don't check config->module_search_paths */
         assert(config->executable != NULL);
+        assert(config->base_executable != NULL);
         assert(config->prefix != NULL);
         assert(config->base_prefix != NULL);
         assert(config->exec_prefix != NULL);
diff --git a/Python/pathconfig.c b/Python/pathconfig.c
index ec67405..79ec4af 100644
--- a/Python/pathconfig.c
+++ b/Python/pathconfig.c
@@ -57,6 +57,7 @@ pathconfig_clear(_PyPathConfig *config)
     CLEAR(config->module_search_path);
     CLEAR(config->home);
     CLEAR(config->program_name);
+    CLEAR(config->base_executable);
 #undef CLEAR
 
     PyMem_SetAllocator(PYMEM_DOMAIN_RAW, &old_alloc);
@@ -89,6 +90,14 @@ pathconfig_calculate(_PyPathConfig *pathconfig, const PyConfig *config)
         status = _PyStatus_NO_MEMORY();
         goto error;
     }
+    if (config->base_executable) {
+        PyMem_RawFree(new_config.base_executable);
+        if (copy_wstr(&new_config.base_executable,
+                      config->base_executable) < 0) {
+            status = _PyStatus_NO_MEMORY();
+            goto error;
+        }
+    }
 
     pathconfig_clear(pathconfig);
     *pathconfig = new_config;
@@ -132,6 +141,7 @@ _PyPathConfig_SetGlobal(const _PyPathConfig *config)
     COPY_ATTR(module_search_path);
     COPY_ATTR(program_name);
     COPY_ATTR(home);
+    COPY_ATTR(base_executable);
 
     pathconfig_clear(&_Py_path_config);
     /* Steal new_config strings; don't clear new_config */
@@ -224,6 +234,9 @@ _PyConfig_SetPathConfig(const PyConfig *config)
     if (copy_wstr(&pathconfig.home, config->home) < 0) {
         goto no_memory;
     }
+    if (copy_wstr(&pathconfig.base_executable, config->base_executable) < 0) {
+        goto no_memory;
+    }
 
     status = _PyPathConfig_SetGlobal(&pathconfig);
     if (_PyStatus_EXCEPTION(status)) {
@@ -321,6 +334,13 @@ config_calculate_pathconfig(PyConfig *config)
         }
     }
 
+    if (config->base_executable == NULL) {
+        if (copy_wstr(&config->base_executable,
+                      pathconfig.base_executable) < 0) {
+            goto no_memory;
+        }
+    }
+
     if (pathconfig.isolated != -1) {
         config->isolated = pathconfig.isolated;
     }
@@ -367,6 +387,14 @@ _PyConfig_InitPathConfig(PyConfig *config)
             return _PyStatus_NO_MEMORY();
         }
     }
+
+    if (config->base_executable == NULL) {
+        if (copy_wstr(&config->base_executable,
+                      config->executable) < 0) {
+            return _PyStatus_NO_MEMORY();
+        }
+    }
+
     return _PyStatus_OK();
 }
 
@@ -434,6 +462,8 @@ Py_SetPath(const wchar_t *path)
     _Py_path_config.home = NULL;
     new_config.program_name = _Py_path_config.program_name;
     _Py_path_config.program_name = NULL;
+    new_config.base_executable = _Py_path_config.base_executable;
+    _Py_path_config.base_executable = NULL;
 
     pathconfig_clear(&_Py_path_config);
     _Py_path_config = new_config;
diff --git a/Python/sysmodule.c b/Python/sysmodule.c
index 1c57561..dc198a5 100644
--- a/Python/sysmodule.c
+++ b/Python/sysmodule.c
@@ -2850,6 +2850,7 @@ _PySys_InitMain(_PyRuntimeState *runtime, PyThreadState *tstate)
     COPY_LIST("path", config->module_search_paths);
 
     SET_SYS_FROM_WSTR("executable", config->executable);
+    SET_SYS_FROM_WSTR("_base_executable", config->base_executable);
     SET_SYS_FROM_WSTR("prefix", config->prefix);
     SET_SYS_FROM_WSTR("base_prefix", config->base_prefix);
     SET_SYS_FROM_WSTR("exec_prefix", config->exec_prefix);