bpo-36763: _Py_RunMain() doesn't call Py_Exit() anymore (GH-13390)

Py_Main() and _Py_RunMain() now return the exitcode rather than
calling Py_Exit(exitcode) when calling PyErr_Print() if the current
exception type is SystemExit.

* Add _Py_HandleSystemExit().
* Add pymain_exit_err_print().
* Add pymain_exit_print().

4 files changed, 116 insertions, 62 deletions

diff --git a/Include/internal/pycore_pylifecycle.h b/Include/internal/pycore_pylifecycle.h
index 0d83acd..4684ebe 100644
--- a/Include/internal/pycore_pylifecycle.h
+++ b/Include/internal/pycore_pylifecycle.h
@@ -100,6 +100,8 @@ PyAPI_FUNC(_PyInitError) _Py_PreInitializeFromCoreConfig(
     const _PyCoreConfig *coreconfig,
     const _PyArgv *args);
 
+PyAPI_FUNC(int) _Py_HandleSystemExit(int *exitcode_p);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/Misc/NEWS.d/next/C API/2019-05-17-19-23-24.bpo-36763.TswmDy.rst b/Misc/NEWS.d/next/C API/2019-05-17-19-23-24.bpo-36763.TswmDy.rst
new file mode 100644
index 0000000..29c0166
--- /dev/null
+++ b/Misc/NEWS.d/next/C API/2019-05-17-19-23-24.bpo-36763.TswmDy.rst
@@ -0,0 +1,3 @@
+``Py_Main()`` now returns the exitcode rather than calling
+``Py_Exit(exitcode)`` when calling ``PyErr_Print()`` if the current
+exception type is ``SystemExit``.
diff --git a/Modules/main.c b/Modules/main.c
index 72546a2..6d4b351 100644
--- a/Modules/main.c
+++ b/Modules/main.c
@@ -94,8 +94,34 @@ stdin_is_interactive(const _PyCoreConfig *config)
 }
 
 
-static PyObject *
-pymain_get_importer(const wchar_t *filename)
+/* Display the current Python exception and return an exitcode */
+static int
+pymain_err_print(int *exitcode_p)
+{
+    int exitcode;
+    if (_Py_HandleSystemExit(&exitcode)) {
+        *exitcode_p = exitcode;
+        return 1;
+    }
+
+    PyErr_Print();
+    return 0;
+}
+
+
+static int
+pymain_exit_err_print(void)
+{
+    int exitcode = 1;
+    pymain_err_print(&exitcode);
+    return exitcode;
+}
+
+
+/* Write an exitcode into *exitcode and return 1 if we have to exit Python.
+   Return 0 otherwise. */
+static int
+pymain_get_importer(const wchar_t *filename, PyObject **importer_p, int *exitcode)
 {
     PyObject *sys_path0 = NULL, *importer;
 
@@ -112,17 +138,18 @@ pymain_get_importer(const wchar_t *filename)
     if (importer == Py_None) {
         Py_DECREF(sys_path0);
         Py_DECREF(importer);
-        return NULL;
+        return 0;
     }
 
     Py_DECREF(importer);
-    return sys_path0;
+    *importer_p = sys_path0;
+    return 0;
 
 error:
     Py_XDECREF(sys_path0);
+
     PySys_WriteStderr("Failed checking if argv[0] is an import path entry\n");
-    PyErr_Print();
-    return NULL;
+    return pymain_err_print(exitcode);
 }
 
 
@@ -217,8 +244,7 @@ pymain_run_command(wchar_t *command, PyCompilerFlags *cf)
 
 error:
     PySys_WriteStderr("Unable to decode the command from the command line:\n");
-    PyErr_Print();
-    return 1;
+    return pymain_exit_err_print();
 }
 
 
@@ -229,44 +255,37 @@ pymain_run_module(const wchar_t *modname, int set_argv0)
     runpy = PyImport_ImportModule("runpy");
     if (runpy == NULL) {
         fprintf(stderr, "Could not import runpy module\n");
-        PyErr_Print();
-        return -1;
+        return pymain_exit_err_print();
     }
     runmodule = PyObject_GetAttrString(runpy, "_run_module_as_main");
     if (runmodule == NULL) {
         fprintf(stderr, "Could not access runpy._run_module_as_main\n");
-        PyErr_Print();
         Py_DECREF(runpy);
-        return -1;
+        return pymain_exit_err_print();
     }
     module = PyUnicode_FromWideChar(modname, wcslen(modname));
     if (module == NULL) {
         fprintf(stderr, "Could not convert module name to unicode\n");
-        PyErr_Print();
         Py_DECREF(runpy);
         Py_DECREF(runmodule);
-        return -1;
+        return pymain_exit_err_print();
     }
     runargs = Py_BuildValue("(Oi)", module, set_argv0);
     if (runargs == NULL) {
         fprintf(stderr,
             "Could not create arguments for runpy._run_module_as_main\n");
-        PyErr_Print();
         Py_DECREF(runpy);
         Py_DECREF(runmodule);
         Py_DECREF(module);
-        return -1;
+        return pymain_exit_err_print();
     }
     result = PyObject_Call(runmodule, runargs, NULL);
-    if (result == NULL) {
-        PyErr_Print();
-    }
     Py_DECREF(runpy);
     Py_DECREF(runmodule);
     Py_DECREF(module);
     Py_DECREF(runargs);
     if (result == NULL) {
-        return -1;
+        return pymain_exit_err_print();
     }
     Py_DECREF(result);
     return 0;
@@ -315,9 +334,8 @@ pymain_run_file(_PyCoreConfig *config, PyCompilerFlags *cf)
 
     /* call pending calls like signal handlers (SIGINT) */
     if (Py_MakePendingCalls() == -1) {
-        PyErr_Print();
         fclose(fp);
-        return 1;
+        return pymain_exit_err_print();
     }
 
     PyObject *unicode, *bytes = NULL;
@@ -343,34 +361,36 @@ pymain_run_file(_PyCoreConfig *config, PyCompilerFlags *cf)
 }
 
 
-static void
-pymain_run_startup(_PyCoreConfig *config, PyCompilerFlags *cf)
+static int
+pymain_run_startup(_PyCoreConfig *config, PyCompilerFlags *cf, int *exitcode)
 {
     const char *startup = _Py_GetEnv(config->use_environment, "PYTHONSTARTUP");
     if (startup == NULL) {
-        return;
+        return 0;
     }
 
     FILE *fp = _Py_fopen(startup, "r");
     if (fp == NULL) {
         int save_errno = errno;
         PySys_WriteStderr("Could not open PYTHONSTARTUP\n");
+
         errno = save_errno;
+        PyErr_SetFromErrnoWithFilename(PyExc_OSError, startup);
 
-        PyErr_SetFromErrnoWithFilename(PyExc_OSError,
-                        startup);
-        PyErr_Print();
-        return;
+        return pymain_err_print(exitcode);
     }
 
     (void) PyRun_SimpleFileExFlags(fp, startup, 0, cf);
     PyErr_Clear();
     fclose(fp);
+    return 0;
 }
 
 
-static void
-pymain_run_interactive_hook(void)
+/* Write an exitcode into *exitcode and return 1 if we have to exit Python.
+   Return 0 otherwise. */
+static int
+pymain_run_interactive_hook(int *exitcode)
 {
     PyObject *sys, *hook, *result;
     sys = PyImport_ImportModule("sys");
@@ -382,7 +402,7 @@ pymain_run_interactive_hook(void)
     Py_DECREF(sys);
     if (hook == NULL) {
         PyErr_Clear();
-        return;
+        return 0;
     }
 
     result = _PyObject_CallNoArg(hook);
@@ -392,11 +412,11 @@ pymain_run_interactive_hook(void)
     }
     Py_DECREF(result);
 
-    return;
+    return 0;
 
 error:
     PySys_WriteStderr("Failed calling sys.__interactivehook__\n");
-    PyErr_Print();
+    return pymain_err_print(exitcode);
 }
 
 
@@ -406,14 +426,20 @@ pymain_run_stdin(_PyCoreConfig *config, PyCompilerFlags *cf)
     if (stdin_is_interactive(config)) {
         config->inspect = 0;
         Py_InspectFlag = 0; /* do exit on SystemExit */
-        pymain_run_startup(config, cf);
-        pymain_run_interactive_hook();
+
+        int exitcode;
+        if (pymain_run_startup(config, cf, &exitcode)) {
+            return exitcode;
+        }
+
+        if (pymain_run_interactive_hook(&exitcode)) {
+            return exitcode;
+        }
     }
 
     /* call pending calls like signal handlers (SIGINT) */
     if (Py_MakePendingCalls() == -1) {
-        PyErr_Print();
-        return 1;
+        return pymain_exit_err_print();
     }
 
     int run = PyRun_AnyFileExFlags(stdin, "<stdin>", 0, cf);
@@ -437,7 +463,9 @@ pymain_repl(_PyCoreConfig *config, PyCompilerFlags *cf, int *exitcode)
 
     config->inspect = 0;
     Py_InspectFlag = 0;
-    pymain_run_interactive_hook();
+    if (pymain_run_interactive_hook(exitcode)) {
+        return;
+    }
 
     int res = PyRun_AnyFileFlags(stdin, "<stdin>", cf);
     *exitcode = (res != 0);
@@ -457,8 +485,11 @@ pymain_run_python(int *exitcode)
            __main__.py, main_importer_path is set to filename and will be
            prepended to sys.path.
 
-           Otherwise, main_importer_path is set to NULL. */
-        main_importer_path = pymain_get_importer(config->run_filename);
+           Otherwise, main_importer_path is left unchanged. */
+        if (pymain_get_importer(config->run_filename, &main_importer_path,
+                                exitcode)) {
+            return;
+        }
     }
 
     if (main_importer_path != NULL) {
@@ -491,11 +522,10 @@ pymain_run_python(int *exitcode)
         *exitcode = pymain_run_command(config->run_command, &cf);
     }
     else if (config->run_module) {
-        *exitcode = (pymain_run_module(config->run_module, 1) != 0);
+        *exitcode = pymain_run_module(config->run_module, 1);
     }
     else if (main_importer_path != NULL) {
-        int sts = pymain_run_module(L"__main__", 0);
-        *exitcode = (sts != 0);
+        *exitcode = pymain_run_module(L"__main__", 0);
     }
     else if (config->run_filename != NULL) {
         *exitcode = pymain_run_file(config, &cf);
@@ -508,8 +538,7 @@ pymain_run_python(int *exitcode)
     goto done;
 
 error:
-    PyErr_Print();
-    *exitcode = 1;
+    *exitcode = pymain_exit_err_print();
 
 done:
     Py_XDECREF(main_importer_path);
diff --git a/Python/pythonrun.c b/Python/pythonrun.c
index bc131fd..d2b2761 100644
--- a/Python/pythonrun.c
+++ b/Python/pythonrun.c
@@ -585,23 +585,31 @@ print_error_text(PyObject *f, int offset, PyObject *text_obj)
     PyFile_WriteString("^\n", f);
 }
 
-static void
-handle_system_exit(void)
-{
-    PyObject *exception, *value, *tb;
-    int exitcode = 0;
 
+int
+_Py_HandleSystemExit(int *exitcode_p)
+{
     int inspect = _PyInterpreterState_GET_UNSAFE()->core_config.inspect;
     if (inspect) {
         /* Don't exit if -i flag was given. This flag is set to 0
          * when entering interactive mode for inspecting. */
-        return;
+        return 0;
     }
 
+    if (!PyErr_ExceptionMatches(PyExc_SystemExit)) {
+        return 0;
+    }
+
+    PyObject *exception, *value, *tb;
     PyErr_Fetch(&exception, &value, &tb);
+
     fflush(stdout);
-    if (value == NULL || value == Py_None)
+
+    int exitcode = 0;
+    if (value == NULL || value == Py_None) {
         goto done;
+    }
+
     if (PyExceptionInstance_Check(value)) {
         /* The error code should be in the `code' attribute. */
         _Py_IDENTIFIER(code);
@@ -615,8 +623,10 @@ handle_system_exit(void)
         /* If we failed to dig out the 'code' attribute,
            just let the else clause below print the error. */
     }
-    if (PyLong_Check(value))
+
+    if (PyLong_Check(value)) {
         exitcode = (int)PyLong_AsLong(value);
+    }
     else {
         PyObject *sys_stderr = _PySys_GetObjectId(&PyId_stderr);
         /* We clear the exception here to avoid triggering the assertion
@@ -633,6 +643,7 @@ handle_system_exit(void)
         PySys_WriteStderr("\n");
         exitcode = 1;
     }
+
  done:
     /* Restore and clear the exception info, in order to properly decref
      * the exception, value, and traceback.      If we just exit instead,
@@ -641,18 +652,28 @@ handle_system_exit(void)
      */
     PyErr_Restore(exception, value, tb);
     PyErr_Clear();
-    Py_Exit(exitcode);
-    /* NOTREACHED */
+    *exitcode_p = exitcode;
+    return 1;
 }
 
+
+static void
+handle_system_exit(void)
+{
+    int exitcode;
+    if (_Py_HandleSystemExit(&exitcode)) {
+        Py_Exit(exitcode);
+    }
+}
+
+
 void
 PyErr_PrintEx(int set_sys_last_vars)
 {
     PyObject *exception, *v, *tb, *hook;
 
-    if (PyErr_ExceptionMatches(PyExc_SystemExit)) {
-        handle_system_exit();
-    }
+    handle_system_exit();
+
     PyErr_Fetch(&exception, &v, &tb);
     if (exception == NULL)
         return;
@@ -686,10 +707,9 @@ PyErr_PrintEx(int set_sys_last_vars)
         stack[2] = tb;
         result = _PyObject_FastCall(hook, stack, 3);
         if (result == NULL) {
+            handle_system_exit();
+
             PyObject *exception2, *v2, *tb2;
-            if (PyErr_ExceptionMatches(PyExc_SystemExit)) {
-                handle_system_exit();
-            }
             PyErr_Fetch(&exception2, &v2, &tb2);
             PyErr_NormalizeException(&exception2, &v2, &tb2);
             /* It should not be possible for exception2 or v2