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bpo-45395: Make custom frozen modules additions instead of replacements. (gh-28778)

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Currently custom modules (the array set on PyImport_FrozenModules) replace all the frozen stdlib modules. That can be problematic and is unlikely to be what the user wants. This change treats the custom frozen modules as additions instead. They take precedence over all other frozen modules except for those needed to bootstrap the import system. If the "code" field of an entry in the custom array is NULL then that frozen module is treated as disabled, which allows a custom entry to disable a frozen stdlib module.

This change allows us to get rid of is_essential_frozen_module() and simplifies the logic for which frozen modules should be ignored.

https://bugs.python.org/issue45395
This commit is contained in:
Eric Snow 2021-10-28 15:04:33 -06:00 • committed by GitHub
parent 66e6b3dcd3
commit 074fa57506
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GPG key ID: 4AEE18F83AFDEB23
10 changed files with 219 additions and 129 deletions
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159
Python/import.c
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@ -1070,27 +1070,6 @@ resolve_module_alias(const char *name, const struct _module_alias *aliases,
/* Frozen modules */
static bool
is_essential_frozen_module(const char *name)
{
/* These modules are necessary to bootstrap the import system. */
if (strcmp(name, "_frozen_importlib") == 0) {
return true;
}
if (strcmp(name, "_frozen_importlib_external") == 0) {
return true;
}
if (strcmp(name, "zipimport") == 0) {
return true;
}
/* This doesn't otherwise have anywhere to find the module.
See frozenmain.c. */
if (strcmp(name, "__main__") == 0) {
return true;
}
return false;
}
static bool
use_frozen(void)
{
@ -1115,26 +1094,76 @@ list_frozen_module_names()
return NULL;
}
bool enabled = use_frozen();
for (const struct _frozen *p = PyImport_FrozenModules; ; p++) {
const struct _frozen *p;
#define ADD_MODULE(name) \
do { \
PyObject *nameobj = PyUnicode_FromString(name); \
if (nameobj == NULL) { \
goto error; \
} \
int res = PyList_Append(names, nameobj); \
Py_DECREF(nameobj); \
if (res != 0) { \
goto error; \
} \
} while(0)
// We always use the bootstrap modules.
for (p = _PyImport_FrozenBootstrap; ; p++) {
if (p->name == NULL) {
break;
}
if (!enabled && !is_essential_frozen_module(p->name)) {
continue;
ADD_MODULE(p->name);
}
// Frozen stdlib modules may be disabled.
for (p = _PyImport_FrozenStdlib; ; p++) {
if (p->name == NULL) {
break;
}
PyObject *name = PyUnicode_FromString(p->name);
if (name == NULL) {
Py_DECREF(names);
return NULL;
if (enabled) {
ADD_MODULE(p->name);
}
int res = PyList_Append(names, name);
Py_DECREF(name);
if (res != 0) {
Py_DECREF(names);
return NULL;
}
for (p = _PyImport_FrozenTest; ; p++) {
if (p->name == NULL) {
break;
}
if (enabled) {
ADD_MODULE(p->name);
}
}
#undef ADD_MODULE
// Add any custom modules.
if (PyImport_FrozenModules != NULL) {
for (p = PyImport_FrozenModules; ; p++) {
if (p->name == NULL) {
break;
}
PyObject *nameobj = PyUnicode_FromString(p->name);
if (nameobj == NULL) {
goto error;
}
int found = PySequence_Contains(names, nameobj);
if (found < 0) {
Py_DECREF(nameobj);
goto error;
}
else if (found) {
Py_DECREF(nameobj);
}
else {
int res = PyList_Append(names, nameobj);
Py_DECREF(nameobj);
if (res != 0) {
goto error;
}
}
}
}
return names;
error:
Py_DECREF(names);
return NULL;
}
typedef enum {
@ -1180,6 +1209,54 @@ set_frozen_error(frozen_status status, PyObject *modname)
}
}
static const struct _frozen *
look_up_frozen(const char *name)
{
const struct _frozen *p;
// We always use the bootstrap modules.
for (p = _PyImport_FrozenBootstrap; ; p++) {
if (p->name == NULL) {
// We hit the end-of-list sentinel value.
break;
}
if (strcmp(name, p->name) == 0) {
return p;
}
}
// Prefer custom modules, if any. Frozen stdlib modules can be
// disabled here by setting "code" to NULL in the array entry.
if (PyImport_FrozenModules != NULL) {
for (p = PyImport_FrozenModules; ; p++) {
if (p->name == NULL) {
break;
}
if (strcmp(name, p->name) == 0) {
return p;
}
}
}
// Frozen stdlib modules may be disabled.
if (use_frozen()) {
for (p = _PyImport_FrozenStdlib; ; p++) {
if (p->name == NULL) {
break;
}
if (strcmp(name, p->name) == 0) {
return p;
}
}
for (p = _PyImport_FrozenTest; ; p++) {
if (p->name == NULL) {
break;
}
if (strcmp(name, p->name) == 0) {
return p;
}
}
}
return NULL;
}
struct frozen_info {
PyObject *nameobj;
const char *data;
@ -1209,19 +1286,9 @@ find_frozen(PyObject *nameobj, struct frozen_info *info)
return FROZEN_BAD_NAME;
}
if (!use_frozen() && !is_essential_frozen_module(name)) {
return FROZEN_DISABLED;
}
const struct _frozen *p;
for (p = PyImport_FrozenModules; ; p++) {
if (p->name == NULL) {
// We hit the end-of-list sentinel value.
return FROZEN_NOT_FOUND;
}
if (strcmp(name, p->name) == 0) {
break;
}
const struct _frozen *p = look_up_frozen(name);
if (p == NULL) {
return FROZEN_NOT_FOUND;
}
if (info != NULL) {
info->nameobj = nameobj; // borrowed