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bpo-36829: Enhance PyErr_WriteUnraisable() (GH-13487) 

PyErr_WriteUnraisable() now displays the exception even if displaying
the traceback failed. Moreover, hold a strong reference to sys.stderr
while using it.

Document that an exception must be set when calling
PyErr_WriteUnraisable(), but don't add an assertion to check it at
runtime.

Cleanup: use longer names for variables and create
write_unraisable_exc_file() subfunction.
This commit is contained in:
Victor Stinner 2019-05-22 18:23:28 +02:00 committed by GitHub
parent d092caf096
commit a58db9628d
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GPG Key ID: 4AEE18F83AFDEB23
3 changed files with 90 additions and 53 deletions
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2
Doc/c-api/exceptions.rst
View File

@ -81,6 +81,8 @@ Printing and clearing
in which the unraisable exception occurred. If possible,
the repr of *obj* will be printed in the warning message.
An exception must be set when calling this function.
Raising exceptions
==================

4
Misc/NEWS.d/next/Core and Builtins/2019-05-22-11-44-41.bpo-36829.ZmpHR9.rst Normal file
View File

@ -0,0 +1,4 @@
:c:func:`PyErr_WriteUnraisable` now displays the exception even if
displaying the traceback failed. Moreover, hold a strong reference to
:data:`sys.stderr` while using it. Document that an exception must be set when
calling :c:func:`PyErr_WriteUnraisable`.

137
Python/errors.c
View File

@ -940,90 +940,121 @@ PyErr_NewExceptionWithDoc(const char *name, const char *doc,
}
/* Call when an exception has occurred but there is no way for Python
to handle it. Examples: exception in __del__ or during GC. */
void
PyErr_WriteUnraisable(PyObject *obj)
static void
write_unraisable_exc_file(PyObject *exc_type, PyObject *exc_value,
PyObject *exc_tb, PyObject *obj, PyObject *file)
{
_Py_IDENTIFIER(__module__);
PyObject *f, *t, *v, *tb;
PyObject *moduleName = NULL;
char* className;
PyErr_Fetch(&t, &v, &tb);
f = _PySys_GetObjectId(&PyId_stderr);
if (f == NULL || f == Py_None)
goto done;
if (obj) {
if (PyFile_WriteString("Exception ignored in: ", f) < 0)
goto done;
if (PyFile_WriteObject(obj, f, 0) < 0) {
if (PyFile_WriteString("Exception ignored in: ", file) < 0) {
return;
}
if (PyFile_WriteObject(obj, file, 0) < 0) {
PyErr_Clear();
if (PyFile_WriteString("<object repr() failed>", f) < 0) {
goto done;
if (PyFile_WriteString("<object repr() failed>", file) < 0) {
return;
}
}
if (PyFile_WriteString("\n", f) < 0)
goto done;
if (PyFile_WriteString("\n", file) < 0) {
return;
}
}
if (PyTraceBack_Print(tb, f) < 0)
goto done;
if (exc_tb != NULL) {
if (PyTraceBack_Print(exc_tb, file) < 0) {
/* continue even if writing the traceback failed */
PyErr_Clear();
}
}
if (!t)
goto done;
if (!exc_type) {
return;
}
assert(PyExceptionClass_Check(t));
className = PyExceptionClass_Name(t);
assert(PyExceptionClass_Check(exc_type));
char* className = PyExceptionClass_Name(exc_type);
if (className != NULL) {
char *dot = strrchr(className, '.');
if (dot != NULL)
if (dot != NULL) {
className = dot+1;
}
}
moduleName = _PyObject_GetAttrId(t, &PyId___module__);
_Py_IDENTIFIER(__module__);
PyObject *moduleName = _PyObject_GetAttrId(exc_type, &PyId___module__);
if (moduleName == NULL || !PyUnicode_Check(moduleName)) {
Py_XDECREF(moduleName);
PyErr_Clear();
if (PyFile_WriteString("<unknown>", f) < 0)
goto done;
if (PyFile_WriteString("<unknown>", file) < 0) {
return;
}
}
else {
if (!_PyUnicode_EqualToASCIIId(moduleName, &PyId_builtins)) {
if (PyFile_WriteObject(moduleName, f, Py_PRINT_RAW) < 0)
goto done;
if (PyFile_WriteString(".", f) < 0)
goto done;
if (PyFile_WriteObject(moduleName, file, Py_PRINT_RAW) < 0) {
Py_DECREF(moduleName);
return;
}
Py_DECREF(moduleName);
if (PyFile_WriteString(".", file) < 0) {
return;
}
}
else {
Py_DECREF(moduleName);
}
}
if (className == NULL) {
if (PyFile_WriteString("<unknown>", f) < 0)
goto done;
if (PyFile_WriteString("<unknown>", file) < 0) {
return;
}
}
else {
if (PyFile_WriteString(className, f) < 0)
goto done;
if (PyFile_WriteString(className, file) < 0) {
return;
}
}
if (v && v != Py_None) {
if (PyFile_WriteString(": ", f) < 0)
goto done;
if (PyFile_WriteObject(v, f, Py_PRINT_RAW) < 0) {
if (exc_value && exc_value != Py_None) {
if (PyFile_WriteString(": ", file) < 0) {
return;
}
if (PyFile_WriteObject(exc_value, file, Py_PRINT_RAW) < 0) {
PyErr_Clear();
if (PyFile_WriteString("<exception str() failed>", f) < 0) {
goto done;
if (PyFile_WriteString("<exception str() failed>", file) < 0) {
return;
}
}
}
if (PyFile_WriteString("\n", f) < 0)
goto done;
if (PyFile_WriteString("\n", file) < 0) {
return;
}
}
done:
Py_XDECREF(moduleName);
Py_XDECREF(t);
Py_XDECREF(v);
Py_XDECREF(tb);
/* Display an unraisable exception into sys.stderr.
Called when an exception has occurred but there is no way for Python to
handle it. For example, when a destructor raises an exception or during
garbage collection (gc.collect()).
An exception must be set when calling this function. */
void
PyErr_WriteUnraisable(PyObject *obj)
{
PyObject *f, *exc_type, *exc_value, *exc_tb;
PyErr_Fetch(&exc_type, &exc_value, &exc_tb);
f = _PySys_GetObjectId(&PyId_stderr);
/* Do nothing if sys.stderr is not available or set to None */
if (f != NULL && f != Py_None) {
write_unraisable_exc_file(exc_type, exc_value, exc_tb, obj, f);
}
Py_XDECREF(exc_type);
Py_XDECREF(exc_value);
Py_XDECREF(exc_tb);
PyErr_Clear(); /* Just in case */
}