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bpo-45061: Detect refcount bug on empty string singleton (GH-28504)

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Detect refcount bugs in C extensions when the empty Unicode string
singleton is destroyed by mistake.

* Move forward declarations to the top of unicodeobject.c.
* Simplifiy unicode_is_singleton().
This commit is contained in:
Victor Stinner 2021-09-21 23:43:09 +02:00 • committed by GitHub
parent 06e1773c8d
commit 86f28372b1
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2 changed files with 40 additions and 20 deletions
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55
Objects/unicodeobject.c
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@ -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_SetFileSystemEncoding()
#include "pycore_pystate.h" // _PyInterpreterState_GET()
#include "pycore_ucnhash.h" // _PyUnicode_Name_CAPI
@ -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)
{
@ -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,
@ -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;
@ -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;
}
}
@ -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)
{