bpo-28411: Isolate PyInterpreterState.modules (#3575)

A bunch of code currently uses PyInterpreterState.modules directly instead of PyImport_GetModuleDict(). This complicates efforts to make changes relative to sys.modules. This patch switches to using PyImport_GetModuleDict() uniformly. Also, a number of related uses of sys.modules are updated for uniformity for the same reason.

Note that this code was already reviewed and merged as part of #1638. I reverted that and am now splitting it up into more focused parts.

1 files changed, 32 insertions, 28 deletions

diff --git a/Python/pylifecycle.c b/Python/pylifecycle.c
index 2aac901..5c8cf5b 100644
--- a/Python/pylifecycle.c
+++ b/Python/pylifecycle.c
@@ -675,9 +675,20 @@ void _Py_InitializeCore(const _PyCoreConfig *config)
     if (!_PyFloat_Init())
         Py_FatalError("Py_InitializeCore: can't init float");
 
-    interp->modules = PyDict_New();
-    if (interp->modules == NULL)
+    PyObject *modules = PyDict_New();
+    if (modules == NULL)
         Py_FatalError("Py_InitializeCore: can't make modules dictionary");
+    interp->modules = modules;
+
+    sysmod = _PySys_BeginInit();
+    if (sysmod == NULL)
+        Py_FatalError("Py_InitializeCore: can't initialize sys");
+    interp->sysdict = PyModule_GetDict(sysmod);
+    if (interp->sysdict == NULL)
+        Py_FatalError("Py_InitializeCore: can't initialize sys dict");
+    Py_INCREF(interp->sysdict);
+    PyDict_SetItemString(interp->sysdict, "modules", modules);
+    _PyImport_FixupBuiltin(sysmod, "sys", modules);
 
     /* Init Unicode implementation; relies on the codec registry */
     if (_PyUnicode_Init() < 0)
@@ -689,7 +700,7 @@ void _Py_InitializeCore(const _PyCoreConfig *config)
     bimod = _PyBuiltin_Init();
     if (bimod == NULL)
         Py_FatalError("Py_InitializeCore: can't initialize builtins modules");
-    _PyImport_FixupBuiltin(bimod, "builtins");
+    _PyImport_FixupBuiltin(bimod, "builtins", modules);
     interp->builtins = PyModule_GetDict(bimod);
     if (interp->builtins == NULL)
         Py_FatalError("Py_InitializeCore: can't initialize builtins dict");
@@ -698,17 +709,6 @@ void _Py_InitializeCore(const _PyCoreConfig *config)
     /* initialize builtin exceptions */
     _PyExc_Init(bimod);
 
-    sysmod = _PySys_BeginInit();
-    if (sysmod == NULL)
-        Py_FatalError("Py_InitializeCore: can't initialize sys");
-    interp->sysdict = PyModule_GetDict(sysmod);
-    if (interp->sysdict == NULL)
-        Py_FatalError("Py_InitializeCore: can't initialize sys dict");
-    Py_INCREF(interp->sysdict);
-    _PyImport_FixupBuiltin(sysmod, "sys");
-    PyDict_SetItemString(interp->sysdict, "modules",
-                         interp->modules);
-
     /* Set up a preliminary stderr printer until we have enough
        infrastructure for the io module in place. */
     pstderr = PyFile_NewStdPrinter(fileno(stderr));
@@ -1211,9 +1211,23 @@ Py_NewInterpreter(void)
 
     /* XXX The following is lax in error checking */
 
-    interp->modules = PyDict_New();
+    PyObject *modules = PyDict_New();
+    if (modules == NULL)
+        Py_FatalError("Py_NewInterpreter: can't make modules dictionary");
+    interp->modules = modules;
 
-    bimod = _PyImport_FindBuiltin("builtins");
+    sysmod = _PyImport_FindBuiltin("sys", modules);
+    if (sysmod != NULL) {
+        interp->sysdict = PyModule_GetDict(sysmod);
+        if (interp->sysdict == NULL)
+            goto handle_error;
+        Py_INCREF(interp->sysdict);
+        PyDict_SetItemString(interp->sysdict, "modules", modules);
+        PySys_SetPath(Py_GetPath());
+        _PySys_EndInit(interp->sysdict);
+    }
+
+    bimod = _PyImport_FindBuiltin("builtins", modules);
     if (bimod != NULL) {
         interp->builtins = PyModule_GetDict(bimod);
         if (interp->builtins == NULL)
@@ -1224,18 +1238,9 @@ Py_NewInterpreter(void)
     /* initialize builtin exceptions */
     _PyExc_Init(bimod);
 
-    sysmod = _PyImport_FindBuiltin("sys");
     if (bimod != NULL && sysmod != NULL) {
         PyObject *pstderr;
 
-        interp->sysdict = PyModule_GetDict(sysmod);
-        if (interp->sysdict == NULL)
-            goto handle_error;
-        Py_INCREF(interp->sysdict);
-        _PySys_EndInit(interp->sysdict);
-        PySys_SetPath(Py_GetPath());
-        PyDict_SetItemString(interp->sysdict, "modules",
-                             interp->modules);
         /* Set up a preliminary stderr printer until we have enough
            infrastructure for the io module in place. */
         pstderr = PyFile_NewStdPrinter(fileno(stderr));
@@ -1911,9 +1916,8 @@ wait_for_thread_shutdown(void)
 {
     _Py_IDENTIFIER(_shutdown);
     PyObject *result;
-    PyThreadState *tstate = PyThreadState_GET();
-    PyObject *threading = PyMapping_GetItemString(tstate->interp->modules,
-                                                  "threading");
+    PyObject *modules = PyImport_GetModuleDict();
+    PyObject *threading = PyMapping_GetItemString(modules, "threading");
     if (threading == NULL) {
         /* threading not imported */
         PyErr_Clear();