libshiboken: Add utility class for stashing Python errors

It encapsulates fetching/restoring errors and uses the old or new exception API depending on version. Task-number: PYSIDE-3067 Change-Id: I6e39d92c7e79fed864b364a90c5bd5b474a41ed6 Reviewed-by: Christian Tismer <tismer@stackless.com>
author: Friedemann Kleint <Friedemann.Kleint@qt.io> 2025-04-17 14:49:57 +0200
committer: Friedemann Kleint <Friedemann.Kleint@qt.io> 2025-05-07 21:10:45 +0200
commit: d8ca812879ad70cd2aa914ea76cd529786deadc6 (patch)
tree: 97140467bca8c9bcda6f492ecb8598c9db136179
parent: cffe2bc71d8e5d88efb879e6fe68c730e547fc4d (diff)
11 files changed, 106 insertions, 58 deletions
diff --git a/sources/pyside6/PySide6/QtCore/typesystem_core_common.xml b/sources/pyside6/PySide6/QtCore/typesystem_core_common.xml
index e0d711313..207844c56 100644
--- a/sources/pyside6/PySide6/QtCore/typesystem_core_common.xml
+++ b/sources/pyside6/PySide6/QtCore/typesystem_core_common.xml
@@ -17,6 +17,7 @@
         <include file-name="pysidemetatype.h" location="global"/>
         <include file-name="pysideutils.h" location="global"/> <!-- QString conversion -->
         <include file-name="signalmanager.h" location="global"/>
+        <include file-name="sbkerrors.h" location="global"/>
         <!-- QtCoreHelper::QGenericReturnArgumentHolder -->
         <include file-name="qtcorehelper.h" location="local"/>
     </extra-includes>
diff --git a/sources/pyside6/PySide6/glue/qtcore.cpp b/sources/pyside6/PySide6/glue/qtcore.cpp
index 689946652..78a25f0a1 100644
--- a/sources/pyside6/PySide6/glue/qtcore.cpp
+++ b/sources/pyside6/PySide6/glue/qtcore.cpp
@@ -433,10 +433,7 @@ static PyObject *qtmsghandler = nullptr;
 static void msgHandlerCallback(QtMsgType type, const QMessageLogContext &ctx, const QString &msg)
 {
     Shiboken::GilState state;
-    PyObject *excType{};
-    PyObject *excValue{};
-    PyObject *excTraceback{};
-    PyErr_Fetch(&excType, &excValue, &excTraceback);
+    Shiboken::Errors::Stash errorStash;
     Shiboken::AutoDecRef arglist(PyTuple_New(3));
     PyTuple_SetItem(arglist, 0, %CONVERTTOPYTHON[QtMsgType](type));
     PyTuple_SetItem(arglist, 1, %CONVERTTOPYTHON[QMessageLogContext &](ctx));
@@ -444,7 +441,6 @@ static void msgHandlerCallback(QtMsgType type, const QMessageLogContext &ctx, co
     const char *data = array.constData();
     PyTuple_SetItem(arglist, 2, %CONVERTTOPYTHON[const char *](data));
     Shiboken::AutoDecRef ret(PyObject_CallObject(qtmsghandler, arglist));
-    PyErr_Restore(excType, excValue, excTraceback);
 }
 // @snippet qt-messagehandler
 
diff --git a/sources/pyside6/libpyside/pyside.cpp b/sources/pyside6/libpyside/pyside.cpp
index 195c000dc..261b2fe77 100644
--- a/sources/pyside6/libpyside/pyside.cpp
+++ b/sources/pyside6/libpyside/pyside.cpp
@@ -30,6 +30,7 @@
 #include <gilstate.h>
 #include <helper.h>
 #include <sbkconverter.h>
+#include <sbkerrors.h>
 #include <sbkstring.h>
 #include <sbkstaticstrings.h>
 #include <sbkfeature_base.h>
@@ -595,10 +596,7 @@ PyObject *getHiddenDataFromQObject(QObject *cppSelf, PyObject *self, PyObject *n
 
     // Search on metaobject (avoid internal attributes started with '__')
     if (!attr) {
-        PyObject *type{};
-        PyObject *value{};
-        PyObject *traceback{};
-        PyErr_Fetch(&type, &value, &traceback);     // This was omitted for a loong time.
+        Shiboken::Errors::Stash errorStash;
 
         int flags = currentSelectId(Py_TYPE(self));
         int snake_flag = flags & 0x01;
@@ -623,8 +621,10 @@ PyObject *getHiddenDataFromQObject(QObject *cppSelf, PyObject *self, PyObject *n
                     if (res) {
                         AutoDecRef elemName(PyObject_GetAttr(res, PySideMagicName::name()));
                         // Note: This comparison works because of interned strings.
-                        if (elemName == name)
+                        if (elemName == name) {
+                            errorStash.release();
                             return res;
+                        }
                         Py_DECREF(res);
                     }
                     PyErr_Clear();
@@ -655,6 +655,7 @@ PyObject *getHiddenDataFromQObject(QObject *cppSelf, PyObject *self, PyObject *n
                     } else if (auto *func = MetaFunction::newObject(cppSelf, i)) {
                         auto *result = reinterpret_cast<PyObject *>(func);
                         PyObject_SetAttr(self, name, result);
+                        errorStash.release();
                         return result;
                     }
                 }
@@ -663,10 +664,10 @@ PyObject *getHiddenDataFromQObject(QObject *cppSelf, PyObject *self, PyObject *n
                 auto *pySignal = reinterpret_cast<PyObject *>(
                     Signal::newObjectFromMethod(cppSelf, self, signalList));
                 PyObject_SetAttr(self, name, pySignal);
+                errorStash.release();
                 return pySignal;
             }
         }
-        PyErr_Restore(type, value, traceback);
     }
     return attr;
 }
diff --git a/sources/pyside6/libpyside/pysidesignal.cpp b/sources/pyside6/libpyside/pysidesignal.cpp
index 5058e3517..a4d1b66b5 100644
--- a/sources/pyside6/libpyside/pysidesignal.cpp
+++ b/sources/pyside6/libpyside/pysidesignal.cpp
@@ -16,6 +16,7 @@
 #include <pep384ext.h>
 #include <sbkconverter.h>
 #include <sbkenum.h>
+#include <sbkerrors.h>
 #include <sbkstaticstrings.h>
 #include <sbkstring.h>
 #include <sbktypefactory.h>
@@ -667,13 +668,9 @@ static PyObject *signalInstanceGetItem(PyObject *self, PyObject *key)
 static inline void warnDisconnectFailed(PyObject *aSlot, const QByteArray &signature)
 {
     if (PyErr_Occurred() != nullptr) { // avoid "%S" invoking str() when an error is set.
-        PyObject *exc{};
-        PyObject *inst{};
-        PyObject *tb{};
-        PyErr_Fetch(&exc, &inst, &tb);
+        Shiboken::Errors::Stash errorStash;
         PyErr_WarnFormat(PyExc_RuntimeWarning, 0, "Failed to disconnect (%s) from signal \"%s\".",
                          Py_TYPE(aSlot)->tp_name, signature.constData());
-        PyErr_Restore(exc, inst, tb);
     } else {
         PyErr_WarnFormat(PyExc_RuntimeWarning, 0, "Failed to disconnect (%S) from signal \"%s\".",
                          aSlot, signature.constData());
diff --git a/sources/pyside6/libpyside/signalmanager.cpp b/sources/pyside6/libpyside/signalmanager.cpp
index 342737c1b..933edd318 100644
--- a/sources/pyside6/libpyside/signalmanager.cpp
+++ b/sources/pyside6/libpyside/signalmanager.cpp
@@ -347,20 +347,15 @@ int SignalManagerPrivate::qtPropertyMetacall(QObject *object,
     if (PyErr_Occurred()) {
         // PYSIDE-2160: An unknown type was reported. Indicated by StopIteration.
         if (PyErr_ExceptionMatches(PyExc_StopIteration)) {
-            PyObject *excType{};
-            PyObject *excValue{};
-            PyObject *excTraceback{};
-            PyErr_Fetch(&excType, &excValue, &excTraceback);
+            Shiboken::Errors::Stash errorStash;
             bool ign = call == QMetaObject::WriteProperty;
             PyErr_WarnFormat(PyExc_RuntimeWarning, 0,
                 ign ? "Unknown property type '%s' of QObject '%s' used in fset"
                     : "Unknown property type '%s' of QObject '%s' used in fget with %R",
-                pp->d->typeName.constData(), metaObject->className(), excValue);
+                pp->d->typeName.constData(), metaObject->className(), errorStash.getException());
             if (PyErr_Occurred())
                 Shiboken::Errors::storeErrorOrPrint();
-            Py_DECREF(excType);
-            Py_DECREF(excValue);
-            Py_XDECREF(excTraceback);
+            errorStash.release();
             return result;
         }
 
diff --git a/sources/pyside6/libpysideqml/pysideqmlmetacallerror.cpp b/sources/pyside6/libpysideqml/pysideqmlmetacallerror.cpp
index a3d2664c4..4e0afa3b2 100644
--- a/sources/pyside6/libpysideqml/pysideqmlmetacallerror.cpp
+++ b/sources/pyside6/libpysideqml/pysideqmlmetacallerror.cpp
@@ -5,6 +5,7 @@
 
 #include <sbkpython.h>
 #include <sbkstring.h>
+#include <sbkerrors.h>
 #include <autodecref.h>
 
 // Remove deprecated MACRO of copysign for MSVC #86286
@@ -40,17 +41,17 @@ std::optional<int> qmlMetaCallErrorHandler(QObject *object)
     if (engine->currentStackFrame == nullptr)
         return {};
 
-    PyObject *errType{};
-    PyObject *errValue{};
-    PyObject *errTraceback{};
-    PyErr_Fetch(&errType, &errValue, &errTraceback);
+    Shiboken::Errors::Stash errorStash;
+    PyObject *errValue = errorStash.getException();
     // PYSIDE-464: The error is only valid before PyErr_Restore,
     // PYSIDE-464: therefore we take local copies.
     Shiboken::AutoDecRef objStr(PyObject_Str(errValue));
     const QString errString = QString::fromUtf8(Shiboken::String::toCString(objStr));
-    const bool isSyntaxError = errType == PyExc_SyntaxError;
-    const bool isTypeError = errType == PyExc_TypeError;
-    PyErr_Restore(errType, errValue, errTraceback);
+    const bool isSyntaxError = errValue != nullptr
+                               && PyErr_GivenExceptionMatches(errValue, PyExc_SyntaxError);
+    const bool isTypeError = errValue != nullptr
+                             && PyErr_GivenExceptionMatches(errValue, PyExc_TypeError);
+    errorStash.restore();
 
     PyErr_Print();    // Note: PyErr_Print clears the error.
 
diff --git a/sources/pyside6/libpysideremoteobjects/pysiderephandler.cpp b/sources/pyside6/libpysideremoteobjects/pysiderephandler.cpp
index bfe085456..aa59c329f 100644
--- a/sources/pyside6/libpysideremoteobjects/pysiderephandler.cpp
+++ b/sources/pyside6/libpysideremoteobjects/pysiderephandler.cpp
@@ -7,6 +7,7 @@
 #include "pysidedynamiccommon_p.h"
 
 #include <pep384ext.h>
+#include <sbkerrors.h>
 #include <sbkstring.h>
 #include <sbktypefactory.h>
 #include <signature.h>
@@ -372,17 +373,11 @@ bool instantiateFromDefaultValue(QVariant &variant, const QString &defaultValue)
     PyObject *pyResult = PyRun_String(code.c_str(), Py_eval_input, pyLocals, pyLocals);
 
     if (!pyResult) {
-        PyObject *ptype = nullptr;
-        PyObject *pvalue = nullptr;
-        PyObject *ptraceback = nullptr;
-        PyErr_Fetch(&ptype, &pvalue, &ptraceback);
-        PyErr_NormalizeException(&ptype, &pvalue, &ptraceback);
+        Shiboken::Errors::Stash errorStash;
         PyErr_Format(PyExc_TypeError,
                      "Failed to generate default value. Error: %s. Problematic code: %s",
-                     Shiboken::String::toCString(PyObject_Str(pvalue)), code.c_str());
-        Py_XDECREF(ptype);
-        Py_XDECREF(pvalue);
-        Py_XDECREF(ptraceback);
+                     Shiboken::String::toCString(PyObject_Str(errorStash.getException())), code.c_str());
+        errorStash.release();
         Py_DECREF(pyLocals);
         return false;
     }
diff --git a/sources/shiboken6/libshiboken/basewrapper.cpp b/sources/shiboken6/libshiboken/basewrapper.cpp
index 25f6ea7c8..a65359a1e 100644
--- a/sources/shiboken6/libshiboken/basewrapper.cpp
+++ b/sources/shiboken6/libshiboken/basewrapper.cpp
@@ -415,12 +415,8 @@ static void SbkDeallocWrapperCommon(PyObject *pyObj, bool canDelete)
         }
     }
 
-    PyObject *error_type{};
-    PyObject *error_value{};
-    PyObject *error_traceback{};
-
     /* Save the current exception, if any. */
-    PyErr_Fetch(&error_type, &error_value, &error_traceback);
+    Shiboken::Errors::Stash errorStash;
 
     if (canDelete) {
         if (sotp->is_multicpp) {
@@ -441,7 +437,7 @@ static void SbkDeallocWrapperCommon(PyObject *pyObj, bool canDelete)
     }
 
     /* Restore the saved exception. */
-    PyErr_Restore(error_type, error_value, error_traceback);
+    errorStash.restore();
 
     if (needTypeDecref)
         Py_DECREF(pyType);
diff --git a/sources/shiboken6/libshiboken/sbkerrors.cpp b/sources/shiboken6/libshiboken/sbkerrors.cpp
index 247fbefc4..6b0600082 100644
--- a/sources/shiboken6/libshiboken/sbkerrors.cpp
+++ b/sources/shiboken6/libshiboken/sbkerrors.cpp
@@ -164,6 +164,17 @@ static void restoreError(ErrorStore &s)
 #endif
 }
 
+static void releaseError(ErrorStore &s)
+{
+    Py_XDECREF(s.exc);
+    s.exc = nullptr;
+#ifdef PEP_OLD_ERR_API
+    Py_XDECREF(s.type);
+    Py_XDECREF(s.traceback);
+    s.type = s.traceback = nullptr;
+#endif
+}
+
 static thread_local ErrorStore savedError;
 
 static bool hasPythonContext()
@@ -209,6 +220,37 @@ PyObject *occurred()
     return PyErr_Occurred();
 }
 
+Stash::Stash() : m_store(std::make_unique<ErrorStore>())
+{
+    fetchError(*m_store);
+}
+
+Stash::~Stash()
+{
+    restore();
+}
+
+PyObject *Stash::getException() const
+{
+    return m_store ? m_store->exc : nullptr;
+}
+
+void Stash::restore()
+{
+    if (m_store) {
+        restoreError(*m_store);
+        m_store.reset();
+    }
+}
+
+void Stash::release()
+{
+    if (m_store) {
+        releaseError(*m_store);
+        m_store.reset();
+    }
+}
+
 } // namespace Errors
 
 namespace Warnings
diff --git a/sources/shiboken6/libshiboken/sbkerrors.h b/sources/shiboken6/libshiboken/sbkerrors.h
index d7247ded4..58576dc7b 100644
--- a/sources/shiboken6/libshiboken/sbkerrors.h
+++ b/sources/shiboken6/libshiboken/sbkerrors.h
@@ -7,6 +7,8 @@
 #include "sbkpython.h"
 #include "shibokenmacros.h"
 
+#include <memory>
+
 /// Craving for C++20 and std::source_location::current()
 #if defined(_MSC_VER)
 #  define SBK_FUNC_INFO     __FUNCSIG__
@@ -35,6 +37,32 @@ public:
 namespace Errors
 {
 
+struct ErrorStore;
+
+/// Temporarily stash an error set in Python
+class Stash
+{
+public:
+    Stash(const Stash &) = delete;
+    Stash &operator=(const Stash &) = delete;
+    Stash(Stash &&) = delete;
+    Stash &operator=(Stash &&) = delete;
+
+    LIBSHIBOKEN_API Stash();
+    LIBSHIBOKEN_API ~Stash();
+
+    LIBSHIBOKEN_API operator bool() const { return getException() != nullptr; }
+    [[nodiscard]] LIBSHIBOKEN_API PyObject *getException() const;
+
+    /// Restore the stored error
+    LIBSHIBOKEN_API void restore();
+    /// Discard the stored error
+    LIBSHIBOKEN_API void release();
+
+private:
+    std::unique_ptr<ErrorStore> m_store;
+};
+
 LIBSHIBOKEN_API void setIndexOutOfBounds(Py_ssize_t value, Py_ssize_t minValue,
                                          Py_ssize_t maxValue);
 LIBSHIBOKEN_API void setInstantiateAbstractClass(const char *name);
diff --git a/sources/shiboken6/libshiboken/sbkfeature_base.cpp b/sources/shiboken6/libshiboken/sbkfeature_base.cpp
index fe32d8ca2..9044539c6 100644
--- a/sources/shiboken6/libshiboken/sbkfeature_base.cpp
+++ b/sources/shiboken6/libshiboken/sbkfeature_base.cpp
@@ -6,6 +6,7 @@
 #include "autodecref.h"
 #include "pep384ext.h"
 #include "sbkenum.h"
+#include "sbkerrors.h"
 #include "sbkstring.h"
 #include "sbkstaticstrings.h"
 #include "sbkstaticstrings_p.h"
@@ -60,8 +61,8 @@ SelectableFeatureHook initSelectableFeature(SelectableFeatureHook func)
 void disassembleFrame(const char *marker)
 {
     Shiboken::GilState gil;
-    PyObject *error_type, *error_value, *error_traceback;
-    PyErr_Fetch(&error_type, &error_value, &error_traceback);
+
+    Shiboken::Errors::Stash errorStash;
     static PyObject *dismodule = PyImport_ImportModule("dis");
     static PyObject *disco = PyObject_GetAttrString(dismodule, "disco");
     static PyObject *const _f_lasti = Shiboken::String::createStaticString("f_lasti");
@@ -84,12 +85,11 @@ void disassembleFrame(const char *marker)
         fprintf(stdout, "%s END line=%ld %s\n\n", marker, line, fname);
     }
 #if PY_VERSION_HEX >= 0x030C0000 && !Py_LIMITED_API
-    if (error_type)
-        PyErr_DisplayException(error_value);
+    if (auto *exc = errorStash.getException())
+        PyErr_DisplayException(exc);
 #endif
     static PyObject *stdout_file = PySys_GetObject("stdout");
     ignore.reset(PyObject_CallMethod(stdout_file, "flush", nullptr));
-    PyErr_Restore(error_type, error_value, error_traceback);
 }
 
 // Python 3.13
@@ -361,15 +361,11 @@ PyObject *mangled_type_getattro(PyTypeObject *type, PyObject *name)
     }
 
     if (!ret && name != ignAttr1 && name != ignAttr2) {
-        PyObject *error_type{}, *error_value{}, *error_traceback{};
-        PyErr_Fetch(&error_type, &error_value, &error_traceback);
+        Shiboken::Errors::Stash errorsStash;
         ret = lookupUnqualifiedOrOldEnum(type, name);
         if (ret) {
-            Py_DECREF(error_type);
-            Py_XDECREF(error_value);
-            Py_XDECREF(error_traceback);
-        } else {
-            PyErr_Restore(error_type, error_value, error_traceback);
+            errorsStash.release();
+            return ret;
         }
     }
     return ret;
author	Friedemann Kleint <Friedemann.Kleint@qt.io>	2025-04-17 14:49:57 +0200
committer	Friedemann Kleint <Friedemann.Kleint@qt.io>	2025-05-07 21:10:45 +0200
commit	d8ca812879ad70cd2aa914ea76cd529786deadc6 (patch)
tree	97140467bca8c9bcda6f492ecb8598c9db136179
parent	cffe2bc71d8e5d88efb879e6fe68c730e547fc4d (diff)