8000 bpo-45061: Detect refcount bug on empty string singleton by vstinner · Pull Request #28504 · python/cpython · GitHub
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bpo-45061: Detect refcount bug on empty string singleton #28504

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Merged
merged 1 commit into from
Sep 21, 2021
Merged

bpo-45061: Detect refcount bug on empty string singleton #28504

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5 changes: 3 additions & 2 deletions Misc/NEWS.d/next/Core and Builtins/2021-09-21-22-27-25.bpo-45061.5IOUf0.rst
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Original file line number Diff line number Diff line change
@@ -1,4 +1,5 @@
Add a deallocator to the bool type to detect refcount bugs in C extensions
which call Py_DECREF(Py_True) or Py_DECREF(Py_False) by mistake. Detect also
refcount bugs when the empty tuple singleton is destroyed by mistake. Patch
by Victor Stinner.
refcount bugs when the empty tuple singleton or the Unicode empty string
singleton is destroyed by mistake.
Patch by Victor Stinner.
55 changes: 37 additions & 18 deletions Objects/unicodeobject.c
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Expand Up @@ -48,6 +48,7 @@ OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
#include "pycore_interp.h" // PyInterpreterState.fs_codec
#include "pycore_object.h" // _PyObject_GC_TRACK()
#include "pycore_pathconfig.h" // _Py_DumpPathConfig()
#include "pycore_pyerrors.h" // _Py_FatalRefcountError()
#include "pycore_pylifecycle.h" // _Py_SetFileS 8000 ystemEncoding()
#include "pycore_pystate.h" // _PyInterpreterState_GET()
#include "pycore_ucnhash.h" // _PyUnicode_Name_CAPI
Expand Down Expand Up @@ -212,6 +213,24 @@ extern "C" {
#endif


/* Forward declaration */
static inline int
_PyUnicodeWriter_WriteCharInline(_PyUnicodeWriter *writer, Py_UCS4 ch);
static inline void
_PyUnicodeWriter_InitWithBuffer(_PyUnicodeWriter *writer, PyObject *buffer);
static PyObject *
unicode_encode_utf8(PyObject *unicode, _Py_error_handler error_handler,
const char *errors);
static PyObject *
unicode_decode_utf8(const char *s, Py_ssize_t size,
_Py_error_handler error_handler, const char *errors,
Py_ssize_t *consumed);
#ifdef Py_DEBUG
static inline int unicode_is_finalizing(void);
static int unicode_is_singleton(PyObject *unicode);
#endif


static struct _Py_unicode_state*
get_unicode_state(void)
{
Expand Down Expand Up @@ -279,19 +298,6 @@ unicode_fill(enum PyUnicode_Kind kind, void *data, Py_UCS4 value,
}


/* Forward declaration */
static inline int
_PyUnicodeWriter_WriteCharInline(_PyUnicodeWriter *writer, Py_UCS4 ch);
static inline void
_PyUnicodeWriter_InitWithBuffer(_PyUnicodeWriter *writer, PyObject *buffer);
static PyObject *
unicode_encode_utf8(PyObject *unicode, _Py_error_handler error_handler,
const char *errors);
static PyObject *
unicode_decode_utf8(const char *s, Py_ssize_t size,
_Py_error_handler error_handler, const char *errors,
Py_ssize_t *consumed);

/* Fast detection of the most frequent whitespace characters */
const unsigned char _Py_ascii_whitespace[] = {
0, 0, 0, 0, 0, 0, 0, 0,
Expand Down Expand Up @@ -1930,6 +1936,12 @@ _PyUnicode_Ready(PyObject *unicode)
static void
unicode_dealloc(PyObject *unicode)
{
#ifdef Py_DEBUG
if (!unicode_is_finalizing() && unicode_is_singleton(unicode)) {
_Py_FatalRefcountError("deallocating an Unicode singleton");
}
#endif

switch (PyUnicode_CHECK_INTERNED(unicode)) {
case SSTATE_NOT_INTERNED:
break;
Expand Down Expand Up @@ -1982,11 +1994,8 @@ unicode_is_singleton(PyObject *unicode)
if (unicode == state->empty_string) {
return 1;
}
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 && state->latin1[ch] == unicode) {
for (Py_ssize_t i = 0; i < 256; i++) {
if (unicode == state->latin1[i]) {
return 1;
}
}
Expand Down Expand Up @@ -15984,6 +15993,16 @@ _PyUnicode_EnableLegacyWindowsFSEncoding(void)
#endif


#ifdef Py_DEBUG
static inline int
unicode_is_finalizing(void)
{
struct _Py_unicode_state *state = get_unicode_state();
return (state->interned == NULL);
}
#endif


void
_PyUnicode_Fini(PyInterpreterState *interp)
{
Expand Down
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