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bpo-42208: Move _PyImport_Cleanup() to pylifecycle.c (GH-23040) 

Move _PyImport_Cleanup() to pylifecycle.c, rename it to
finalize_modules(), split it (200 lines) into many smaller
sub-functions and cleanup the code.
This commit is contained in:
Victor Stinner 2020-10-30 18:03:28 +01:00 committed by GitHub
parent 8b3414818f
commit dff1ad5090
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GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 290 additions and 230 deletions
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227
Python/import.c
View File

@ -406,233 +406,6 @@ import_ensure_initialized(PyThreadState *tstate, PyObject *mod, PyObject *name)
}
/* List of names to clear in sys */
static const char * const sys_deletes[] = {
"path", "argv", "ps1", "ps2",
"last_type", "last_value", "last_traceback",
"path_hooks", "path_importer_cache", "meta_path",
"__interactivehook__",
NULL
};
static const char * const sys_files[] = {
"stdin", "__stdin__",
"stdout", "__stdout__",
"stderr", "__stderr__",
NULL
};
/* Un-initialize things, as good as we can */
void
_PyImport_Cleanup(PyThreadState *tstate)
{
PyInterpreterState *interp = tstate->interp;
PyObject *modules = interp->modules;
if (modules == NULL) {
/* Already done */
return;
}
/* Delete some special variables first. These are common
places where user values hide and people complain when their
destructors fail. Since the modules containing them are
deleted *last* of all, they would come too late in the normal
destruction order. Sigh. */
/* XXX Perhaps these precautions are obsolete. Who knows? */
int verbose = _PyInterpreterState_GetConfig(interp)->verbose;
if (verbose) {
PySys_WriteStderr("# clear builtins._\n");
}
if (PyDict_SetItemString(interp->builtins, "_", Py_None) < 0) {
PyErr_WriteUnraisable(NULL);
}
const char * const *p;
for (p = sys_deletes; *p != NULL; p++) {
if (verbose) {
PySys_WriteStderr("# clear sys.%s\n", *p);
}
if (PyDict_SetItemString(interp->sysdict, *p, Py_None) < 0) {
PyErr_WriteUnraisable(NULL);
}
}
for (p = sys_files; *p != NULL; p+=2) {
if (verbose) {
PySys_WriteStderr("# restore sys.%s\n", *p);
}
PyObject *value = _PyDict_GetItemStringWithError(interp->sysdict,
*(p+1));
if (value == NULL) {
if (_PyErr_Occurred(tstate)) {
PyErr_WriteUnraisable(NULL);
}
value = Py_None;
}
if (PyDict_SetItemString(interp->sysdict, *p, value) < 0) {
PyErr_WriteUnraisable(NULL);
}
}
/* We prepare a list which will receive (name, weakref) tuples of
modules when they are removed from sys.modules. The name is used
for diagnosis messages (in verbose mode), while the weakref helps
detect those modules which have been held alive. */
PyObject *weaklist = PyList_New(0);
if (weaklist == NULL) {
PyErr_WriteUnraisable(NULL);
}
#define STORE_MODULE_WEAKREF(name, mod) \
if (weaklist != NULL) { \
PyObject *wr = PyWeakref_NewRef(mod, NULL); \
if (wr) { \
PyObject *tup = PyTuple_Pack(2, name, wr); \
if (!tup || PyList_Append(weaklist, tup) < 0) { \
PyErr_WriteUnraisable(NULL); \
} \
Py_XDECREF(tup); \
Py_DECREF(wr); \
} \
else { \
PyErr_WriteUnraisable(NULL); \
} \
}
#define CLEAR_MODULE(name, mod) \
if (PyModule_Check(mod)) { \
if (verbose && PyUnicode_Check(name)) { \
PySys_FormatStderr("# cleanup[2] removing %U\n", name); \
} \
STORE_MODULE_WEAKREF(name, mod); \
if (PyObject_SetItem(modules, name, Py_None) < 0) { \
PyErr_WriteUnraisable(NULL); \
} \
}
/* Remove all modules from sys.modules, hoping that garbage collection
can reclaim most of them. */
if (PyDict_CheckExact(modules)) {
Py_ssize_t pos = 0;
PyObject *key, *value;
while (PyDict_Next(modules, &pos, &key, &value)) {
CLEAR_MODULE(key, value);
}
}
else {
PyObject *iterator = PyObject_GetIter(modules);
if (iterator == NULL) {
PyErr_WriteUnraisable(NULL);
}
else {
PyObject *key;
while ((key = PyIter_Next(iterator))) {
PyObject *value = PyObject_GetItem(modules, key);
if (value == NULL) {
PyErr_WriteUnraisable(NULL);
continue;
}
CLEAR_MODULE(key, value);
Py_DECREF(value);
Py_DECREF(key);
}
if (PyErr_Occurred()) {
PyErr_WriteUnraisable(NULL);
}
Py_DECREF(iterator);
}
}
/* Clear the modules dict. */
if (PyDict_CheckExact(modules)) {
PyDict_Clear(modules);
}
else {
_Py_IDENTIFIER(clear);
if (_PyObject_CallMethodIdNoArgs(modules, &PyId_clear) == NULL) {
PyErr_WriteUnraisable(NULL);
}
}
/* Restore the original builtins dict, to ensure that any
user data gets cleared. */
PyObject *dict = PyDict_Copy(interp->builtins);
if (dict == NULL) {
PyErr_WriteUnraisable(NULL);
}
PyDict_Clear(interp->builtins);
if (PyDict_Update(interp->builtins, interp->builtins_copy)) {
_PyErr_Clear(tstate);
}
Py_XDECREF(dict);
/* Collect references */
_PyGC_CollectNoFail(tstate);
/* Dump GC stats before it's too late, since it uses the warnings
machinery. */
_PyGC_DumpShutdownStats(tstate);
/* Now, if there are any modules left alive, clear their globals to
minimize potential leaks. All C extension modules actually end
up here, since they are kept alive in the interpreter state.
The special treatment of "builtins" here is because even
when it's not referenced as a module, its dictionary is
referenced by almost every module's __builtins__. Since
deleting a module clears its dictionary (even if there are
references left to it), we need to delete the "builtins"
module last. Likewise, we don't delete sys until the very
end because it is implicitly referenced (e.g. by print). */
if (weaklist != NULL) {
Py_ssize_t i;
/* Since dict is ordered in CPython 3.6+, modules are saved in
importing order. First clear modules imported later. */
for (i = PyList_GET_SIZE(weaklist) - 1; i >= 0; i--) {
PyObject *tup = PyList_GET_ITEM(weaklist, i);
PyObject *name = PyTuple_GET_ITEM(tup, 0);
PyObject *mod = PyWeakref_GET_OBJECT(PyTuple_GET_ITEM(tup, 1));
if (mod == Py_None)
continue;
assert(PyModule_Check(mod));
dict = PyModule_GetDict(mod);
if (dict == interp->builtins || dict == interp->sysdict)
continue;
Py_INCREF(mod);
if (verbose && PyUnicode_Check(name)) {
PySys_FormatStderr("# cleanup[3] wiping %U\n", name);
}
_PyModule_Clear(mod);
Py_DECREF(mod);
}
Py_DECREF(weaklist);
}
/* Next, delete sys and builtins (in that order) */
if (verbose) {
PySys_FormatStderr("# cleanup[3] wiping sys\n");
}
_PyModule_ClearDict(interp->sysdict);
if (verbose) {
PySys_FormatStderr("# cleanup[3] wiping builtins\n");
}
_PyModule_ClearDict(interp->builtins);
/* Clear module dict copies stored in the interpreter state */
_PyInterpreterState_ClearModules(interp);
/* Clear and delete the modules directory. Actual modules will
still be there only if imported during the execution of some
destructor. */
interp->modules = NULL;
Py_DECREF(modules);
/* Once more */
_PyGC_CollectNoFail(tstate);
#undef CLEAR_MODULE
#undef STORE_MODULE_WEAKREF
}
/* Helper for pythonrun.c -- return magic number and tag. */
long

293
Python/pylifecycle.c
View File

@ -8,7 +8,6 @@
#include "pycore_ceval.h" // _PyEval_FiniGIL()
#include "pycore_context.h" // _PyContext_Init()
#include "pycore_fileutils.h" // _Py_ResetForceASCII()
#include "pycore_import.h" // _PyImport_Cleanup()
#include "pycore_initconfig.h" // _PyStatus_OK()
#include "pycore_object.h" // _PyDebug_PrintTotalRefs()
#include "pycore_pathconfig.h" // _PyConfig_WritePathConfig()
@ -1192,6 +1191,292 @@ Py_Initialize(void)
}
static void
finalize_modules_delete_special(PyThreadState *tstate, int verbose)
{
// List of names to clear in sys
static const char * const sys_deletes[] = {
"path", "argv", "ps1", "ps2",
"last_type", "last_value", "last_traceback",
"path_hooks", "path_importer_cache", "meta_path",
"__interactivehook__",
NULL
};
static const char * const sys_files[] = {
"stdin", "__stdin__",
"stdout", "__stdout__",
"stderr", "__stderr__",
NULL
};
PyInterpreterState *interp = tstate->interp;
if (verbose) {
PySys_WriteStderr("# clear builtins._\n");
}
if (PyDict_SetItemString(interp->builtins, "_", Py_None) < 0) {
PyErr_WriteUnraisable(NULL);
}
const char * const *p;
for (p = sys_deletes; *p != NULL; p++) {
if (verbose) {
PySys_WriteStderr("# clear sys.%s\n", *p);
}
if (PyDict_SetItemString(interp->sysdict, *p, Py_None) < 0) {
PyErr_WriteUnraisable(NULL);
}
}
for (p = sys_files; *p != NULL; p+=2) {
const char *name = p[0];
const char *orig_name = p[1];
if (verbose) {
PySys_WriteStderr("# restore sys.%s\n", name);
}
PyObject *value = _PyDict_GetItemStringWithError(interp->sysdict,
orig_name);
if (value == NULL) {
if (_PyErr_Occurred(tstate)) {
PyErr_WriteUnraisable(NULL);
}
value = Py_None;
}
if (PyDict_SetItemString(interp->sysdict, name, value) < 0) {
PyErr_WriteUnraisable(NULL);
}
}
}
static PyObject*
finalize_remove_modules(PyObject *modules, int verbose)
{
PyObject *weaklist = PyList_New(0);
if (weaklist == NULL) {
PyErr_WriteUnraisable(NULL);
}
#define STORE_MODULE_WEAKREF(name, mod) \
if (weaklist != NULL) { \
PyObject *wr = PyWeakref_NewRef(mod, NULL); \
if (wr) { \
PyObject *tup = PyTuple_Pack(2, name, wr); \
if (!tup || PyList_Append(weaklist, tup) < 0) { \
PyErr_WriteUnraisable(NULL); \
} \
Py_XDECREF(tup); \
Py_DECREF(wr); \
} \
else { \
PyErr_WriteUnraisable(NULL); \
} \
}
#define CLEAR_MODULE(name, mod) \
if (PyModule_Check(mod)) { \
if (verbose && PyUnicode_Check(name)) { \
PySys_FormatStderr("# cleanup[2] removing %U\n", name); \
} \
STORE_MODULE_WEAKREF(name, mod); \
if (PyObject_SetItem(modules, name, Py_None) < 0) { \
PyErr_WriteUnraisable(NULL); \
} \
}
if (PyDict_CheckExact(modules)) {
Py_ssize_t pos = 0;
PyObject *key, *value;
while (PyDict_Next(modules, &pos, &key, &value)) {
CLEAR_MODULE(key, value);
}
}
else {
PyObject *iterator = PyObject_GetIter(modules);
if (iterator == NULL) {
PyErr_WriteUnraisable(NULL);
}
else {
PyObject *key;
while ((key = PyIter_Next(iterator))) {
PyObject *value = PyObject_GetItem(modules, key);
if (value == NULL) {
PyErr_WriteUnraisable(NULL);
continue;
}
CLEAR_MODULE(key, value);
Py_DECREF(value);
Py_DECREF(key);
}
if (PyErr_Occurred()) {
PyErr_WriteUnraisable(NULL);
}
Py_DECREF(iterator);
}
}
#undef CLEAR_MODULE
#undef STORE_MODULE_WEAKREF
return weaklist;
}
static void
finalize_clear_modules_dict(PyObject *modules)
{
if (PyDict_CheckExact(modules)) {
PyDict_Clear(modules);
}
else {
_Py_IDENTIFIER(clear);
if (_PyObject_CallMethodIdNoArgs(modules, &PyId_clear) == NULL) {
PyErr_WriteUnraisable(NULL);
}
}
}
static void
finalize_restore_builtins(PyThreadState *tstate)
{
PyInterpreterState *interp = tstate->interp;
PyObject *dict = PyDict_Copy(interp->builtins);
if (dict == NULL) {
PyErr_WriteUnraisable(NULL);
}
PyDict_Clear(interp->builtins);
if (PyDict_Update(interp->builtins, interp->builtins_copy)) {
_PyErr_Clear(tstate);
}
Py_XDECREF(dict);
}
static void
finalize_modules_clear_weaklist(PyInterpreterState *interp,
PyObject *weaklist, int verbose)
{
// First clear modules imported later
for (Py_ssize_t i = PyList_GET_SIZE(weaklist) - 1; i >= 0; i--) {
PyObject *tup = PyList_GET_ITEM(weaklist, i);
PyObject *name = PyTuple_GET_ITEM(tup, 0);
PyObject *mod = PyWeakref_GET_OBJECT(PyTuple_GET_ITEM(tup, 1));
if (mod == Py_None) {
continue;
}
assert(PyModule_Check(mod));
PyObject *dict = PyModule_GetDict(mod);
if (dict == interp->builtins || dict == interp->sysdict) {
continue;
}
Py_INCREF(mod);
if (verbose && PyUnicode_Check(name)) {
PySys_FormatStderr("# cleanup[3] wiping %U\n", name);
}
_PyModule_Clear(mod);
Py_DECREF(mod);
}
}
static void
finalize_clear_sys_builtins_dict(PyInterpreterState *interp, int verbose)
{
// Clear sys dict
if (verbose) {
PySys_FormatStderr("# cleanup[3] wiping sys\n");
}
_PyModule_ClearDict(interp->sysdict);
// Clear builtins dict
if (verbose) {
PySys_FormatStderr("# cleanup[3] wiping builtins\n");
}
_PyModule_ClearDict(interp->builtins);
}
/* Clear modules, as good as we can */
static void
finalize_modules(PyThreadState *tstate)
{
PyInterpreterState *interp = tstate->interp;
PyObject *modules = interp->modules;
if (modules == NULL) {
// Already done
return;
}
int verbose = _PyInterpreterState_GetConfig(interp)->verbose;
// Delete some special builtins._ and sys attributes first. These are
// common places where user values hide and people complain when their
// destructors fail. Since the modules containing them are
// deleted *last* of all, they would come too late in the normal
// destruction order. Sigh.
//
// XXX Perhaps these precautions are obsolete. Who knows?
finalize_modules_delete_special(tstate, verbose);
// Remove all modules from sys.modules, hoping that garbage collection
// can reclaim most of them: set all sys.modules values to None.
//
// We prepare a list which will receive (name, weakref) tuples of
// modules when they are removed from sys.modules. The name is used
// for diagnosis messages (in verbose mode), while the weakref helps
// detect those modules which have been held alive.
PyObject *weaklist = finalize_remove_modules(modules, verbose);
// Clear the modules dict
finalize_clear_modules_dict(modules);
// Restore the original builtins dict, to ensure that any
// user data gets cleared.
finalize_restore_builtins(tstate);
// Collect garbage
_PyGC_CollectNoFail(tstate);
// Dump GC stats before it's too late, since it uses the warnings
// machinery.
_PyGC_DumpShutdownStats(tstate);
if (weaklist != NULL) {
// Now, if there are any modules left alive, clear their globals to
// minimize potential leaks. All C extension modules actually end
// up here, since they are kept alive in the interpreter state.
//
// The special treatment of "builtins" here is because even
// when it's not referenced as a module, its dictionary is
// referenced by almost every module's __builtins__. Since
// deleting a module clears its dictionary (even if there are
// references left to it), we need to delete the "builtins"
// module last. Likewise, we don't delete sys until the very
// end because it is implicitly referenced (e.g. by print).
//
// Since dict is ordered in CPython 3.6+, modules are saved in
// importing order. First clear modules imported later.
finalize_modules_clear_weaklist(interp, weaklist, verbose);
Py_DECREF(weaklist);
}
// Clear sys and builtins modules dict
finalize_clear_sys_builtins_dict(interp, verbose);
// Clear module dict copies stored in the interpreter state:
// clear PyInterpreterState.modules_by_index and
// clear PyModuleDef.m_base.m_copy (of extensions not using the multi-phase
// initialization API)
_PyInterpreterState_ClearModules(interp);
// Clear and delete the modules directory. Actual modules will
// still be there only if imported during the execution of some
// destructor.
Py_SETREF(interp->modules, NULL);
// Collect garbage once more
_PyGC_CollectNoFail(tstate);
}
/* Flush stdout and stderr */
static int
@ -1210,6 +1495,7 @@ file_is_closed(PyObject *fobj)
return r > 0;
}
static int
flush_std_files(void)
{
@ -1417,7 +1703,7 @@ Py_FinalizeEx(void)
PyGC_Collect();
/* Destroy all modules */
_PyImport_Cleanup(tstate);
finalize_modules(tstate);
/* Print debug stats if any */
_PyEval_Fini();
@ -1660,7 +1946,8 @@ Py_EndInterpreter(PyThreadState *tstate)
Py_FatalError("not the last thread");
}
_PyImport_Cleanup(tstate);
finalize_modules(tstate);
finalize_interp_clear(tstate);
finalize_interp_delete(tstate);
}