use Python 3.12 PyErr_GetRaisedException() API

Author: wjakob

cmake/darwin-ld-cpython.sym

@@ -132,6 +132,7 @@
 -U _PyErr_FormatV
 -U _PyErr_GetExcInfo
 -U _PyErr_GetHandledException
+-U _PyErr_GetRaisedException
 -U _PyErr_GivenExceptionMatches
 -U _PyErr_NewException
 -U _PyErr_NewExceptionWithDoc
@@ -161,6 +162,7 @@
 -U _PyErr_SetInterruptEx
 -U _PyErr_SetNone
 -U _PyErr_SetObject
+-U _PyErr_SetRaisedException
 -U _PyErr_SetString
 -U _PyErr_SyntaxLocation
 -U _PyErr_SyntaxLocationEx

docs/api_core.rst

@@ -1095,7 +1095,7 @@ the reference section on :ref:`class binding <class_binding>`.
 
       Returns a handle to the exception value
 
-   .. cpp:function:: handle traceback() const
+   .. cpp:function:: object traceback() const
 
       Returns a handle to the exception's traceback object
 

include/nanobind/nb_error.h

@@ -10,11 +10,21 @@
 NAMESPACE_BEGIN(NB_NAMESPACE)
 
 /// RAII wrapper that temporarily clears any Python error state
+#if PY_VERSION_HEX >= 0x030C0000
+struct error_scope {
+    error_scope() { value = PyErr_GetRaisedException(); }
+    ~error_scope() { PyErr_SetRaisedException(value); }
+private:
+    PyObject *value;
+};
+#else
 struct error_scope {
     error_scope() { PyErr_Fetch(&type, &value, &trace); }
     ~error_scope() { PyErr_Restore(type, value, trace); }
+private:
     PyObject *type, *value, *trace;
 };
+#endif
 
 /// Wraps a Python error state as a C++ exception
 class NB_EXPORT python_error : public std::exception {
@@ -25,7 +35,11 @@ class NB_EXPORT python_error : public std::exception {
     NB_EXPORT_SHARED ~python_error() override;
 
     bool matches(handle exc) const noexcept {
+#if PY_VERSION_HEX < 0x030C0000
         return PyErr_GivenExceptionMatches(m_type, exc.ptr()) != 0;
+#else
+        return PyErr_GivenExceptionMatches(m_value, exc.ptr()) != 0;
+#endif
     }
 
     /// Move the error back into the Python domain. This may only be called
@@ -42,16 +56,28 @@ class NB_EXPORT python_error : public std::exception {
         PyErr_WriteUnraisable(context.ptr());
     }
 
-    handle type() const { return m_type; }
     handle value() const { return m_value; }
-    handle trace() const { return m_trace; }
+
+#if PY_VERSION_HEX < 0x030C0000
+    handle type() const { return m_type; }
+    object traceback() const { return steal(m_traceback); }
+#else
+    handle type() const { return value().type(); }
+    object traceback() const { return steal(PyException_GetTraceback(m_value)); }
+#endif
+    [[deprecated]]
+    object trace() const { return traceback(); }
 
     NB_EXPORT_SHARED const char *what() const noexcept override;
 
 private:
+#if PY_VERSION_HEX < 0x030C0000
     mutable PyObject *m_type = nullptr;
     mutable PyObject *m_value = nullptr;
-    mutable PyObject *m_trace = nullptr;
+    mutable PyObject *m_traceback = nullptr;
+#else
+    mutable PyObject *m_value = nullptr;
+#endif
     mutable char *m_what = nullptr;
 };
 

src/error.cpp

@@ -18,46 +18,102 @@ Buffer buf(128);
 
 NAMESPACE_END(detail)
 
+#if PY_VERSION_HEX >= 0x030C0000
 python_error::python_error() {
-    PyErr_Fetch(&m_type, &m_value, &m_trace);
+    m_value = PyErr_GetRaisedException();
+    check(m_value,
+          "nanobind::python_error::python_error(): error indicator unset!");
+}
+
+python_error::~python_error() {
+    if (m_value) {
+        gil_scoped_acquire acq;
+        /* With GIL held */ {
+            // Clear error status in case the following executes Python code
+            error_scope scope;
+            Py_DECREF(m_value);
+        }
+    }
+
+    free(m_what);
+}
+
+python_error::python_error(const python_error &e)
+    : std::exception(e), m_value(e.m_value) {
+    if (m_value) {
+        gil_scoped_acquire acq;
+        Py_INCREF(m_value);
+    }
+    if (e.m_what)
+        m_what = NB_STRDUP(e.m_what);
+}
+
+python_error::python_error(python_error &&e) noexcept
+    : std::exception(e), m_value(e.m_value), m_what(e.m_what) {
+    e.m_value = nullptr;
+    e.m_what = nullptr;
+}
+
+void python_error::restore() noexcept {
+    check(m_value,
+          "nanobind::python_error::restore(): error was already restored!");
+
+    PyErr_SetRaisedException(m_value);
+    m_value = nullptr;
+}
+
+#else /* Exception handling for Python 3.11 and older versions */
+
+python_error::python_error() {
+    PyErr_Fetch(&m_type, &m_value, &m_traceback);
     check(m_type,
           "nanobind::python_error::python_error(): error indicator unset!");
 }
 
 python_error::~python_error() {
-    if (m_type || m_value || m_trace) {
+    if (m_type) {
         gil_scoped_acquire acq;
         /* With GIL held */ {
             // Clear error status in case the following executes Python code
             error_scope scope;
-            Py_XDECREF(m_type);
             Py_XDECREF(m_value);
-            Py_XDECREF(m_trace);
+            Py_XDECREF(m_type);
+            Py_XDECREF(m_traceback);
         }
     }
     free(m_what);
 }
 
 python_error::python_error(const python_error &e)
     : std::exception(e), m_type(e.m_type), m_value(e.m_value),
-      m_trace(e.m_trace) {
-    if (m_type || m_value || m_trace) {
+      m_traceback(e.m_traceback) {
+    if (m_type) {
         gil_scoped_acquire acq;
-        Py_XINCREF(m_type);
+        Py_INCREF(m_type);
         Py_XINCREF(m_value);
-        Py_XINCREF(m_trace);
+        Py_XINCREF(m_traceback);
     }
     if (e.m_what)
         m_what = NB_STRDUP(e.m_what);
 }
 
 python_error::python_error(python_error &&e) noexcept
     : std::exception(e), m_type(e.m_type), m_value(e.m_value),
-      m_trace(e.m_trace), m_what(e.m_what) {
-    e.m_type = e.m_value = e.m_trace = nullptr;
+      m_traceback(e.m_traceback), m_what(e.m_what) {
+    e.m_type = e.m_value = e.m_traceback = nullptr;
     e.m_what = nullptr;
 }
 
+void python_error::restore() noexcept {
+    check(m_type,
+          "nanobind::python_error::restore(): error was already restored!");
+
+    PyErr_Restore(m_type, m_value, m_traceback);
+    m_type = m_value = m_traceback = nullptr;
+}
+
+#endif
+
 const char *python_error::what() const noexcept {
     using detail::buf;
 
@@ -71,23 +127,30 @@ const char *python_error::what() const noexcept {
     if (m_what)
         return m_what;
 
-    PyErr_NormalizeException(&m_type, &m_value, &m_trace);
+#if PY_VERSION_HEX < 0x030C0000
+    PyErr_NormalizeException(&m_type, &m_value, &m_traceback);
     check(m_type,
           "nanobind::python_error::what(): PyNormalize_Exception() failed!");
 
-    if (m_trace) {
-        if (PyException_SetTraceback(m_value, m_trace) < 0)
+    if (m_traceback) {
+        if (PyException_SetTraceback(m_value, m_traceback) < 0)
             PyErr_Clear();
     }
 
+    handle exc_type = m_type, exc_value = m_value;
+#else
+    handle exc_value = m_value, exc_type = exc_value.type();
+#endif
+    object exc_traceback = traceback();
+
 #if defined(Py_LIMITED_API) || defined(PYPY_VERSION)
     object mod = module_::import_("traceback"),
-           result = mod.attr("format_exception")(handle(m_type), handle(m_value), handle(m_trace));
+           result = mod.attr("format_exception")(exc_type, exc_value, exc_traceback);
     m_what = NB_STRDUP(borrow<str>(str("\n").attr("join")(result)).c_str());
 #else
     buf.clear();
-    if (m_trace) {
-        PyTracebackObject *to = (PyTracebackObject *) m_trace;
+    if (exc_traceback.is_valid()) {
+        PyTracebackObject *to = (PyTracebackObject *) exc_traceback.ptr();
 
         // Get the deepest trace possible
         while (to->tb_next)
@@ -130,28 +193,20 @@ const char *python_error::what() const noexcept {
         }
     }
 
-    if (m_type) {
-        object name = handle(m_type).attr("__name__");
+    if (exc_type.is_valid()) {
+        object name = exc_type.attr("__name__");
         buf.put_dstr(borrow<str>(name).c_str());
         buf.put(": ");
     }
 
-    if (m_value)
+    if (exc_value.is_valid())
         buf.put_dstr(str(m_value).c_str());
     m_what = buf.copy();
 #endif
 
     return m_what;
 }
 
-void python_error::restore() noexcept {
-    check(m_type,
-          "nanobind::python_error::restore(): error was already restored!");
-
-    PyErr_Restore(m_type, m_value, m_trace);
-    m_type = m_value = m_trace = nullptr;
-}
-
 builtin_exception::builtin_exception(exception_type type, const char *what)
     : std::runtime_error(what ? what : ""), m_type(type) { }
 builtin_exception::~builtin_exception() { }