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bpo-40521: Disable Unicode caches in isolated subinterpreters #19933

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merged 1 commit into from
May 5, 2020
Merged

bpo-40521: Disable Unicode caches in isolated subinterpreters #19933

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16 changes: 16 additions & 0 deletions Objects/typeobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -56,6 +56,11 @@ static size_t method_cache_misses = 0;
static size_t method_cache_collisions = 0;
#endif

/* bpo-40521: Interned strings are shared by all subinterpreters */
#ifndef EXPERIMENTAL_ISOLATED_SUBINTERPRETERS
# define INTERN_NAME_STRINGS
#endif

/* alphabetical order */
_Py_IDENTIFIER(__abstractmethods__);
_Py_IDENTIFIER(__class__);
Expand Down Expand Up @@ -3418,6 +3423,7 @@ type_setattro(PyTypeObject *type, PyObject *name, PyObject *value)
if (name == NULL)
return -1;
}
#ifdef INTERN_NAME_STRINGS
if (!PyUnicode_CHECK_INTERNED(name)) {
PyUnicode_InternInPlace(&name);
if (!PyUnicode_CHECK_INTERNED(name)) {
Expand All @@ -3427,6 +3433,7 @@ type_setattro(PyTypeObject *type, PyObject *name, PyObject *value)
return -1;
}
}
#endif
}
else {
/* Will fail in _PyObject_GenericSetAttrWithDict. */
Expand Down Expand Up @@ -7531,10 +7538,17 @@ _PyTypes_InitSlotDefs(void)
for (slotdef *p = slotdefs; p->name; p++) {
/* Slots must be ordered by their offset in the PyHeapTypeObject. */
assert(!p[1].name || p->offset <= p[1].offset);
#ifdef INTERN_NAME_STRINGS
p->name_strobj = PyUnicode_InternFromString(p->name);
if (!p->name_strobj || !PyUnicode_CHECK_INTERNED(p->name_strobj)) {
return _PyStatus_NO_MEMORY();
}
#else
p->name_strobj = PyUnicode_FromString(p->name);
if (!p->name_strobj) {
return _PyStatus_NO_MEMORY();
}
#endif
}
slotdefs_initialized = 1;
return _PyStatus_OK();
Expand All @@ -7559,7 +7573,9 @@ update_slot(PyTypeObject *type, PyObject *name)
int offset;

assert(PyUnicode_CheckExact(name));
#ifdef INTERN_NAME_STRINGS
assert(PyUnicode_CHECK_INTERNED(name));
#endif

assert(slotdefs_initialized);
pp = ptrs;
Expand Down
78 changes: 63 additions & 15 deletions Objects/unicodeobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -198,6 +198,11 @@ extern "C" {
# define OVERALLOCATE_FACTOR 4
#endif

/* bpo-40521: Interned strings are shared by all interpreters. */
#ifndef EXPERIMENTAL_ISOLATED_SUBINTERPRETERS
# define INTERNED_STRINGS
#endif

/* This dictionary holds all interned unicode strings. Note that references
to strings in this dictionary are *not* counted in the string's ob_refcnt.
When the interned string reaches a refcnt of 0 the string deallocation
Expand All @@ -206,7 +211,9 @@ extern "C" {
Another way to look at this is that to say that the actual reference
count of a string is: s->ob_refcnt + (s->state ? 2 : 0)
*/
#ifdef INTERNED_STRINGS
static PyObject *interned = NULL;
#endif

/* The empty Unicode object is shared to improve performance. */
static PyObject *unicode_empty = NULL;
Expand Down Expand Up @@ -281,9 +288,16 @@ unicode_decode_utf8(const char *s, Py_ssize_t size,
/* List of static strings. */
static _Py_Identifier *static_strings = NULL;

/* bpo-40521: Latin1 singletons are shared by all interpreters. */
#ifndef EXPERIMENTAL_ISOLATED_SUBINTERPRETERS
# define LATIN1_SINGLETONS
#endif

#ifdef LATIN1_SINGLETONS
/* Single character Unicode strings in the Latin-1 range are being
shared as well. */
static PyObject *unicode_latin1[256] = {NULL};
#endif

/* Fast detection of the most frequent whitespace characters */
const unsigned char _Py_ascii_whitespace[] = {
Expand Down Expand Up @@ -662,6 +676,7 @@ unicode_result_ready(PyObject *unicode)
return unicode_empty;
}

#ifdef LATIN1_SINGLETONS
if (length == 1) {
const void *data = PyUnicode_DATA(unicode);
int kind = PyUnicode_KIND(unicode);
Expand All @@ -683,6 +698,7 @@ unicode_result_ready(PyObject *unicode)
}
}
}
#endif

assert(_PyUnicode_CheckConsistency(unicode, 1));
return unicode;
Expand Down Expand Up @@ -1913,10 +1929,12 @@ unicode_dealloc(PyObject *unicode)
case SSTATE_INTERNED_MORTAL:
/* revive dead object temporarily for DelItem */
Py_SET_REFCNT(unicode, 3);
#ifdef INTERNED_STRINGS
if (PyDict_DelItem(interned, unicode) != 0) {
_PyErr_WriteUnraisableMsg("deletion of interned string failed",
NULL);
}
#endif
break;

case SSTATE_INTERNED_IMMORTAL:
Expand Down Expand Up @@ -1944,15 +1962,18 @@ unicode_dealloc(PyObject *unicode)
static int
unicode_is_singleton(PyObject *unicode)
{
PyASCIIObject *ascii = (PyASCIIObject *)unicode;
if (unicode == unicode_empty)
if (unicode == unicode_empty) {
return 1;
}
#ifdef LATIN1_SINGLETONS
PyASCIIObject *ascii = (PyASCIIObject *)unicode;
if (ascii->state.kind != PyUnicode_WCHAR_KIND && ascii->length == 1)
{
Py_UCS4 ch = PyUnicode_READ_CHAR(unicode, 0);
if (ch < 256 && unicode_latin1[ch] == unicode)
return 1;
}
#endif
return 0;
}
#endif
Expand Down Expand Up @@ -2094,16 +2115,28 @@ unicode_write_cstr(PyObject *unicode, Py_ssize_t index,
static PyObject*
get_latin1_char(unsigned char ch)
{
PyObject *unicode = unicode_latin1[ch];
PyObject *unicode;

#ifdef LATIN1_SINGLETONS
unicode = unicode_latin1[ch];
if (unicode) {
Py_INCREF(unicode);
return unicode;
}
#endif

unicode = PyUnicode_New(1, ch);
if (!unicode) {
unicode = PyUnicode_New(1, ch);
if (!unicode)
return NULL;
PyUnicode_1BYTE_DATA(unicode)[0] = ch;
assert(_PyUnicode_CheckConsistency(unicode, 1));
unicode_latin1[ch] = unicode;
return NULL;
}

PyUnicode_1BYTE_DATA(unicode)[0] = ch;
assert(_PyUnicode_CheckConsistency(unicode, 1));

#ifdef LATIN1_SINGLETONS
Py_INCREF(unicode);
unicode_latin1[ch] = unicode;
#endif
return unicode;
}

Expand Down Expand Up @@ -11270,7 +11303,6 @@ int
_PyUnicode_EqualToASCIIId(PyObject *left, _Py_Identifier *right)
{
PyObject *right_uni;
Py_hash_t hash;

assert(_PyUnicode_CHECK(left));
assert(right->string);
Expand Down Expand Up @@ -11302,10 +11334,12 @@ _PyUnicode_EqualToASCIIId(PyObject *left, _Py_Identifier *right)
if (PyUnicode_CHECK_INTERNED(left))
return 0;

#ifdef INTERNED_STRINGS
assert(_PyUnicode_HASH(right_uni) != -1);
hash = _PyUnicode_HASH(left);
Py_hash_t hash = _PyUnicode_HASH(left);
if (hash != -1 && hash != _PyUnicode_HASH(right_uni))
return 0;
#endif

return unicode_compare_eq(left, right_uni);
}
Expand Down Expand Up @@ -15487,43 +15521,55 @@ void
PyUnicode_InternInPlace(PyObject **p)
{
PyObject *s = *p;
PyObject *t;
#ifdef Py_DEBUG
assert(s != NULL);
assert(_PyUnicode_CHECK(s));
#else
if (s == NULL || !PyUnicode_Check(s))
if (s == NULL || !PyUnicode_Check(s)) {
return;
}
#endif

/* If it's a subclass, we don't really know what putting
it in the interned dict might do. */
if (!PyUnicode_CheckExact(s))
if (!PyUnicode_CheckExact(s)) {
return;
if (PyUnicode_CHECK_INTERNED(s))
}

if (PyUnicode_CHECK_INTERNED(s)) {
return;
}

#ifdef INTERNED_STRINGS
if (interned == NULL) {
interned = PyDict_New();
if (interned == NULL) {
PyErr_Clear(); /* Don't leave an exception */
return;
}
}

PyObject *t;
Py_ALLOW_RECURSION
t = PyDict_SetDefault(interned, s, s);
Py_END_ALLOW_RECURSION

if (t == NULL) {
PyErr_Clear();
return;
}

if (t != s) {
Py_INCREF(t);
Py_SETREF(*p, t);
return;
}

/* The two references in interned are not counted by refcnt.
The deallocator will take care of this */
Py_SET_REFCNT(s, Py_REFCNT(s) - 2);
_PyUnicode_STATE(s).interned = SSTATE_INTERNED_MORTAL;
#endif
}

void
Expand Down Expand Up @@ -16109,9 +16155,11 @@ _PyUnicode_Fini(PyThreadState *tstate)

Py_CLEAR(unicode_empty);

#ifdef LATIN1_SINGLETONS
for (Py_ssize_t i = 0; i < 256; i++) {
Py_CLEAR(unicode_latin1[i]);
}
#endif
_PyUnicode_ClearStaticStrings();
}

Expand Down