gh-134604: Fix tracemalloc crash with subinterpreters

Include/internal/pycore_tracemalloc.h

@@ -43,7 +43,7 @@ __attribute__((packed))
 tracemalloc_frame{
  /* filename cannot be NULL: "<unknown>" is used if the Python frame
  filename is NULL */
-PyObject *filename;
+char *filename;
  unsigned int lineno;
 };
 #ifdef _MSC_VER

Lib/test/test__interpreters.py

@@ -3,6 +3,7 @@
 import pickle
 from textwrap import dedent
 import threading
+import tracemalloc
 import unittest
 
 from test import support
@@ -1098,5 +1099,34 @@ def script(spam, /):
  _interpreters.run_func(self.id, script)
 
 
+class TestTracemallocWithInterpreters(TestBase):
+ def setUp(self):
+ if tracemalloc.is_tracing():
+ self.skipTest("tracemalloc must be stopped before the test")
+
+ tracemalloc.start(1)
+
+ def tearDown(self):
+ tracemalloc.stop()
+ super().tearDown()
+
+ def test_trace_interp_start_frames(self):
+ interpid = _interpreters.create()
+ # check that tracing captures frames created by the new interpreter
+ self.assertNotEqual(
+ tracemalloc.take_snapshot().statistics("filename"),
+ []
+ )
+ _interpreters.destroy(interpid)
+
+ def test_trace_interp_frames(self):
+ interpid = _interpreters.create()
+ _interpreters.run_string(interpid, "def f(): ...")
+ stats = tracemalloc.take_snapshot().statistics("filename")
+ # check that the last frame is the string run in the interpreter
+ self.assertEqual(stats[-1].traceback._frames[0][0], "<string>")
+ _interpreters.destroy(interpid)
+
+
 if __name__ == '__main__':
  unittest.main()

Misc/NEWS.d/next/Core_and_Builtins/2025-05-25-11-09-35.gh-issue-134604.AGZhQe.rst

@@ -0,0 +1 @@
+Fix crash when using :mod:`tracemalloc` with sub-interpreters.

Python/tracemalloc.c

@@ -126,20 +126,20 @@ set_reentrant(int reentrant)
 
 
 static Py_uhash_t
-hashtable_hash_pyobject(const void *key)
+hashtable_hash_filename(const void *key)
 {
-PyObject *obj = (PyObject *)key;
- return PyObject_Hash(obj);
+char *obj = (char *)key;
+ return Py_HashBuffer(obj, strlen(obj));
 }
 
 
 static int
 hashtable_compare_unicode(const void *key1, const void *key2)
 {
-PyObject *obj1 = (PyObject *)key1;
-PyObject *obj2 = (PyObject *)key2;
+char *obj1 = (char *)key1;
+char *obj2 = (char *)key2;
  if (obj1 != NULL && obj2 != NULL){
- return (PyUnicode_Compare(obj1, obj2) == 0);
+ return (strcmp(obj1, obj2) == 0);
  }
  else{
  return obj1 == obj2;
@@ -209,8 +209,7 @@ hashtable_compare_traceback(const void *key1, const void *key2)
  if (frame1->lineno != frame2->lineno){
  return 0;
  }
- if (frame1->filename != frame2->filename){
- assert(PyUnicode_Compare(frame1->filename, frame2->filename) != 0);
+ if (strcmp(frame1->filename, frame2->filename) != 0){
  return 0;
  }
  }
@@ -222,15 +221,15 @@ static void
 tracemalloc_get_frame(_PyInterpreterFrame *pyframe, frame_t *frame)
 {
  assert(PyStackRef_CodeCheck(pyframe->f_executable));
- frame->filename = &_Py_STR(anon_unknown);
+ frame->filename = "<unknown>";
 
  int lineno = PyUnstable_InterpreterFrame_GetLine(pyframe);
  if (lineno < 0){
  lineno = 0;
  }
  frame->lineno = (unsigned int)lineno;
 
- PyObject *filename = filename = _PyFrame_GetCode(pyframe)->co_filename;
+ PyObject *filename = _PyFrame_GetCode(pyframe)->co_filename;
  if (filename == NULL){
 #ifdef TRACE_DEBUG
  tracemalloc_error("failed to get the filename of the code object");
@@ -245,18 +244,42 @@ tracemalloc_get_frame(_PyInterpreterFrame *pyframe, frame_t *frame)
  return;
  }
 
+ /* Copy filename to be held by tracemalloc. Subinterpreter frames may
+ disappear at any time, so instead of holding a reference, we must copy
+ the filename to ensure we don't lose it. */
+ Py_ssize_t filename_len;
+ const char *frame_filename = PyUnicode_AsUTF8AndSize(filename,
+ &filename_len);
+ if (frame_filename == NULL){
+#ifdef TRACE_DEBUG
+ tracemalloc_error("Could not convert filename to UTF8");
+#endif
+ return;
+ }
+
  /* intern the filename */
+ char *filename_copy;
  _Py_hashtable_entry_t *entry;
- entry = _Py_hashtable_get_entry(tracemalloc_filenames, filename);
+
+ entry = _Py_hashtable_get_entry(tracemalloc_filenames, frame_filename);
  if (entry != NULL){
-filename = (PyObject *)entry->key;
+filename_copy = (char *)entry->key;
  }
  else{
- /* tracemalloc_filenames is responsible to keep a reference
- to the filename */
- if (_Py_hashtable_set(tracemalloc_filenames, Py_NewRef(filename),
+ /* tracemalloc_filenames is responsible for keeping a copy
+ of the filename */
+ filename_copy = (char*)raw_malloc(filename_len + 1);
+ if (filename_copy == NULL){
+#ifdef TRACE_DEBUG
+ tracemalloc_error("filename copy allocation failed");
+#endif
+ return;
+ }
+
+ strcpy(filename_copy, frame_filename);
+ if (_Py_hashtable_set(tracemalloc_filenames, filename_copy,
  NULL) < 0){
-Py_DECREF(filename);
+raw_free(filename_copy);
 #ifdef TRACE_DEBUG
  tracemalloc_error("failed to intern the filename");
 #endif
@@ -265,7 +288,7 @@ tracemalloc_get_frame(_PyInterpreterFrame *pyframe, frame_t *frame)
  }
 
  /* the tracemalloc_filenames table keeps a reference to the filename */
- frame->filename = filename;
+ frame->filename = filename_copy;
 }
 
 
@@ -281,7 +304,8 @@ traceback_hash(traceback_t *traceback)
  x = 0x345678UL;
  frame = traceback->frames;
  while (--len >= 0){
- y = (Py_uhash_t)PyObject_Hash(frame->filename);
+ y = (Py_uhash_t)Py_HashBuffer(frame->filename,
+ strlen(frame->filename));
  y ^= (Py_uhash_t)frame->lineno;
  frame++;
 
@@ -698,19 +722,9 @@ tracemalloc_raw_realloc(void *ctx, void *ptr, size_t new_size)
 }
 
 
-static void
-tracemalloc_clear_filename(void *value)
-{
- PyObject *filename = (PyObject *)value;
- Py_DECREF(filename);
-}
-
-
 static void
 tracemalloc_clear_traces_unlocked(void)
 {
- // Clearing tracemalloc_filenames requires the GIL to call Py_DECREF()
- _Py_AssertHoldsTstate();
 
  set_reentrant(1);
 
@@ -737,9 +751,9 @@ _PyTraceMalloc_Init(void)
  return _PyStatus_NO_MEMORY();
  }
 
- tracemalloc_filenames = hashtable_new(hashtable_hash_pyobject,
+ tracemalloc_filenames = hashtable_new(hashtable_hash_filename,
  hashtable_compare_unicode,
-tracemalloc_clear_filename, NULL);
+raw_free, NULL);
 
  tracemalloc_tracebacks = hashtable_new(hashtable_hash_traceback,
  hashtable_compare_traceback,
@@ -756,8 +770,7 @@ _PyTraceMalloc_Init(void)
 
  tracemalloc_empty_traceback.nframe = 1;
  tracemalloc_empty_traceback.total_nframe = 1;
- /* borrowed reference */
- tracemalloc_empty_traceback.frames[0].filename = &_Py_STR(anon_unknown);
+ tracemalloc_empty_traceback.frames[0].filename = "<unknown>"
  tracemalloc_empty_traceback.frames[0].lineno = 0;
  tracemalloc_empty_traceback.hash = traceback_hash(&tracemalloc_empty_traceback);
 
@@ -888,7 +901,8 @@ frame_to_pyobject(frame_t *frame)
  return NULL;
  }
 
- PyTuple_SET_ITEM(frame_obj, 0, Py_NewRef(frame->filename));
+ PyObject *filename = PyUnicode_FromString(frame->filename);
+ PyTuple_SET_ITEM(frame_obj, 0, filename);
 
  PyObject *lineno_obj = PyLong_FromUnsignedLong(frame->lineno);
  if (lineno_obj == NULL){
@@ -1144,7 +1158,7 @@ static void
 _PyMem_DumpFrame(int fd, frame_t * frame)
 {
  PUTS(fd, " File \"");
-_Py_DumpASCII(fd, frame->filename);
+PUTS(fd, frame->filename);
  PUTS(fd, "\", line ");
  _Py_DumpDecimal(fd, frame->lineno);
  PUTS(fd, "\n");