8000 bpo-42923: Dump extension modules on fatal error (GH-24207) · python/cpython@250035d · GitHub
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bpo-42923: Dump extension modules on fatal error (GH-24207)
The Py_FatalError() function and the faulthandler module now dump the list of extension modules on a fatal error. Add _Py_DumpExtensionModules() and _PyModule_IsExtension() internal functions.
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8 files changed

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‎Include/internal/pycore_pyerrors.h

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@@ -84,6 +84,8 @@ PyAPI_FUNC(PyObject *) _PyErr_FormatFromCauseTstate(
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PyAPI_FUNC(int) _PyErr_CheckSignalsTstate(PyThreadState *tstate);
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PyAPI_FUNC(void) _Py_DumpExtensionModules(int fd, PyInterpreterState *interp);
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#ifdef __cplusplus
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}
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#endif

‎Include/moduleobject.h

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@@ -84,6 +84,12 @@ typedef struct PyModuleDef{
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freefunc m_free;
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} PyModuleDef;
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// Internal C API
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#ifdef Py_BUILD_CORE
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extern int _PyModule_IsExtension(PyObject *obj);
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#endif
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#ifdef __cplusplus
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}
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#endif

‎Lib/test/test_capi.py

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@@ -556,6 +556,16 @@ def test_fatal_error(self):
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self.assertIn('Fatal Python error: test_fatal_error: MESSAGE\n',
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err)
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match = re.search('^Extension modules:(.*)$', err, re.MULTILINE)
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if not match:
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self.fail(f"Cannot find 'Extension modules:' in {err!r}")
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modules = set(match.group(1).strip().split(', '))
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# Test _PyModule_IsExtension(): the list doesn't have to
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# be exhaustive.
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for name in ('sys', 'builtins', '_imp', '_thread', '_weakref',
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'_io', 'marshal', '_signal', '_abc', '_testcapi'):
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self.assertIn(name, modules)
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class TestPendingCalls(unittest.TestCase):
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‎Lib/test/test_faulthandler.py

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Original file line numberDiff line numberDiff line change
@@ -2,6 +2,7 @@
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import datetime
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import faulthandler
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import os
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import re
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import signal
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import subprocess
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import sys
@@ -329,6 +330,24 @@ def test_disable(self):
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"%r is present in %r" % (not_expected, stderr))
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self.assertNotEqual(exitcode, 0)
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@skip_segfault_on_android
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def test_dump_ext_modules(self):
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code = """
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import faulthandler
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faulthandler.enable()
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faulthandler._sigsegv()
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"""
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stderr, exitcode = self.get_output(code)
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stderr = '\n'.join(stderr)
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match = re.search('^Extension modules:(.*)$', stderr, re.MULTILINE)
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if not match:
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self.fail(f"Cannot find 'Extension modules:' in {stderr!r}")
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modules = set(match.group(1).strip().split(', '))
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# Only check for a few extensions, the list doesn't have to be
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# exhaustive.
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for ext in ('sys', 'builtins', '_io', 'faulthandler'):
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self.assertIn(ext, modules)
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def test_is_enabled(self):
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orig_stderr = sys.stderr
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try:

‎Misc/NEWS.d/next/Library/2021-01-13-12-15-13.bpo-42923.zBiNls.rst

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,2 @@
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The :c:func:`Py_FatalError` function and the :mod:`faulthandler` module now
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dump the list of extension modules on a fatal error.

‎Modules/faulthandler.c

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@@ -1,5 +1,6 @@
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#include "Python.h"
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#include "pycore_initconfig.h" // _PyStatus_ERR
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#include "pycore_pyerrors.h" // _Py_DumpExtensionModules
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#include "pycore_traceback.h" // _Py_DumpTracebackThreads
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#include <signal.h>
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#include <object.h>
@@ -349,6 +350,8 @@ faulthandler_fatal_error(int signum)
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faulthandler_dump_traceback(fd, fatal_error.all_threads,
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fatal_error.interp);
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_Py_DumpExtensionModules(fd, fatal_error.interp);
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errno = save_errno;
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#ifdef MS_WINDOWS
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if (signum == SIGSEGV) {

‎Objects/moduleobject.c

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Original file line numberDiff line numberDiff line change
@@ -35,6 +35,19 @@ PyTypeObject PyModuleDef_Type = {
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};
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int
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_PyModule_IsExtension(PyObject *obj)
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{
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if (!PyModule_Check(obj)) {
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return 0;
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}
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PyModuleObject *module = (PyModuleObject*)obj;
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struct PyModuleDef *def = module->md_def;
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return (def != NULL && def->m_methods != NULL);
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}
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PyObject*
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PyModuleDef_Init(struct PyModuleDef* def)
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{

‎Python/pylifecycle.c

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Original file line numberDiff line numberDiff line change
@@ -2496,6 +2496,45 @@ fatal_error_exit(int status)
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}
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// Dump the list of extension modules of sys.modules into fd file descriptor.
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// This function is called by a signal handler in faulthandler: avoid memory
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// allocations and keep the implementation simple. For example, the list
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// is not sorted on purpose.
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void
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_Py_DumpExtensionModules(int fd, PyInterpreterState *interp)
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{
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if (interp == NULL) {
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return;
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}
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PyObject *modules = interp->modules;
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if (!PyDict_Check(modules)) {
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return;
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}
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PUTS(fd, "\nExtension modules: ");
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Py_ssize_t pos = 0;
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PyObject *key, *value;
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int comma = 0;
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while (PyDict_Next(modules, &pos, &key, &value)) {
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if (!PyUnicode_Check(key)) {
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continue;
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}
2523+
if (!_PyModule_IsExtension(value)) {
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continue;
2525+
}
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2527+
if (comma) {
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PUTS(fd, ", ");
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}
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comma = 1;
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_Py_DumpASCII(fd, key);
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}
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PUTS(fd, "\n");
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}
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static void _Py_NO_RETURN
25002539
fatal_error(int fd, int header, const char *prefix, const char *msg,
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int status)
@@ -2557,6 +2596,8 @@ fatal_error(int fd, int header, const char *prefix, const char *msg,
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_Py_FatalError_DumpTracebacks(fd, interp, tss_tstate);
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}
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_Py_DumpExtensionModules(fd, interp);
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/* The main purpose of faulthandler is to display the traceback.
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This function already did its best to display a traceback.
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Disable faulthandler to prevent writing a second traceback

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