gh-102192: Replace PyErr_Fetch/Restore etc by more efficient alternatives (#102769)

Author: iritkatriel

Python/errors.c

@@ -666,17 +666,15 @@ _PyErr_ChainExceptions(PyObject *typ, PyObject *val, PyObject *tb)
     }
 
     if (_PyErr_Occurred(tstate)) {
-        PyObject *typ2, *val2, *tb2;
-        _PyErr_Fetch(tstate, &typ2, &val2, &tb2);
         _PyErr_NormalizeException(tstate, &typ, &val, &tb);
         if (tb != NULL) {
             PyException_SetTraceback(val, tb);
             Py_DECREF(tb);
         }
         Py_DECREF(typ);
-        _PyErr_NormalizeException(tstate, &typ2, &val2, &tb2);
-        PyException_SetContext(val2, val);
-        _PyErr_Restore(tstate, typ2, val2, tb2);
+        PyObject *exc2 = _PyErr_GetRaisedException(tstate);
+        PyException_SetContext(exc2, val);
+        _PyErr_SetRaisedException(tstate, exc2);
     }
     else {
         _PyErr_Restore(tstate, typ, val, tb);
@@ -757,27 +755,15 @@ static PyObject *
 _PyErr_FormatVFromCause(PyThreadState *tstate, PyObject *exception,
                         const char *format, va_list vargs)
 {
-    PyObject *exc, *val, *val2, *tb;
-
     assert(_PyErr_Occurred(tstate));
-    _PyErr_Fetch(tstate, &exc, &val, &tb);
-    _PyErr_NormalizeException(tstate, &exc, &val, &tb);
-    if (tb != NULL) {
-        PyException_SetTraceback(val, tb);
-        Py_DECREF(tb);
-    }
-    Py_DECREF(exc);
+    PyObject *exc = _PyErr_GetRaisedException(tstate);
     assert(!_PyErr_Occurred(tstate));
-
     _PyErr_FormatV(tstate, exception, format, vargs);
-
-    _PyErr_Fetch(tstate, &exc, &val2, &tb);
-    _PyErr_NormalizeException(tstate, &exc, &val2, &tb);
-    PyException_SetCause(val2, Py_NewRef(val));
-    PyException_SetContext(val2, Py_NewRef(val));
-    Py_DECREF(val);
-    _PyErr_Restore(tstate, exc, val2, tb);
-
+    PyObject *exc2 = _PyErr_GetRaisedException(tstate);
+    PyException_SetCause(exc2, Py_NewRef(exc));
+    PyException_SetContext(exc2, Py_NewRef(exc));
+    Py_DECREF(exc);
+    _PyErr_SetRaisedException(tstate, exc2);
     return NULL;
 }
 
@@ -1698,19 +1684,18 @@ static void
 PyErr_SyntaxLocationObjectEx(PyObject *filename, int lineno, int col_offset,
                              int end_lineno, int end_col_offset)
 {
-    PyObject *exc, *v, *tb, *tmp;
     PyThreadState *tstate = _PyThreadState_GET();
 
     /* add attributes for the line number and filename for the error */
-    _PyErr_Fetch(tstate, &exc, &v, &tb);
-    _PyErr_NormalizeException(tstate, &exc, &v, &tb);
+    PyObject *exc = _PyErr_GetRaisedException(tstate);
     /* XXX check that it is, indeed, a syntax error. It might not
      * be, though. */
-    tmp = PyLong_FromLong(lineno);
-    if (tmp == NULL)
+    PyObject *tmp = PyLong_FromLong(lineno);
+    if (tmp == NULL) {
         _PyErr_Clear(tstate);
+    }
     else {
-        if (PyObject_SetAttr(v, &_Py_ID(lineno), tmp)) {
+        if (PyObject_SetAttr(exc, &_Py_ID(lineno), tmp)) {
             _PyErr_Clear(tstate);
         }
         Py_DECREF(tmp);
@@ -1722,7 +1707,7 @@ PyErr_SyntaxLocationObjectEx(PyObject *filename, int lineno, int col_offset,
             _PyErr_Clear(tstate);
         }
     }
-    if (PyObject_SetAttr(v, &_Py_ID(offset), tmp ? tmp : Py_None)) {
+    if (PyObject_SetAttr(exc, &_Py_ID(offset), tmp ? tmp : Py_None)) {
         _PyErr_Clear(tstate);
     }
     Py_XDECREF(tmp);
@@ -1734,7 +1719,7 @@ PyErr_SyntaxLocationObjectEx(PyObject *filename, int lineno, int col_offset,
             _PyErr_Clear(tstate);
         }
     }
-    if (PyObject_SetAttr(v, &_Py_ID(end_lineno), tmp ? tmp : Py_None)) {
+    if (PyObject_SetAttr(exc, &_Py_ID(end_lineno), tmp ? tmp : Py_None)) {
         _PyErr_Clear(tstate);
     }
     Py_XDECREF(tmp);
@@ -1746,20 +1731,20 @@ PyErr_SyntaxLocationObjectEx(PyObject *filename, int lineno, int col_offset,
             _PyErr_Clear(tstate);
         }
     }
-    if (PyObject_SetAttr(v, &_Py_ID(end_offset), tmp ? tmp : Py_None)) {
+    if (PyObject_SetAttr(exc, &_Py_ID(end_offset), tmp ? tmp : Py_None)) {
         _PyErr_Clear(tstate);
     }
     Py_XDECREF(tmp);
 
     tmp = NULL;
     if (filename != NULL) {
-        if (PyObject_SetAttr(v, &_Py_ID(filename), filename)) {
+        if (PyObject_SetAttr(exc, &_Py_ID(filename), filename)) {
             _PyErr_Clear(tstate);
         }
 
         tmp = PyErr_ProgramTextObject(filename, lineno);
         if (tmp) {
-            if (PyObject_SetAttr(v, &_Py_ID(text), tmp)) {
+            if (PyObject_SetAttr(exc, &_Py_ID(text), tmp)) {
                 _PyErr_Clear(tstate);
             }
             Py_DECREF(tmp);
@@ -1768,17 +1753,17 @@ PyErr_SyntaxLocationObjectEx(PyObject *filename, int lineno, int col_offset,
             _PyErr_Clear(tstate);
         }
     }
-    if (exc != PyExc_SyntaxError) {
-        if (_PyObject_LookupAttr(v, &_Py_ID(msg), &tmp) < 0) {
+    if ((PyObject *)Py_TYPE(exc) != PyExc_SyntaxError) {
+        if (_PyObject_LookupAttr(exc, &_Py_ID(msg), &tmp) < 0) {
             _PyErr_Clear(tstate);
         }
         else if (tmp) {
             Py_DECREF(tmp);
         }
         else {
-            tmp = PyObject_Str(v);
+            tmp = PyObject_Str(exc);
             if (tmp) {
-                if (PyObject_SetAttr(v, &_Py_ID(msg), tmp)) {
+                if (PyObject_SetAttr(exc, &_Py_ID(msg), tmp)) {
                     _PyErr_Clear(tstate);
                 }
                 Py_DECREF(tmp);
@@ -1788,19 +1773,19 @@ PyErr_SyntaxLocationObjectEx(PyObject *filename, int lineno, int col_offset,
             }
         }
 
-        if (_PyObject_LookupAttr(v, &_Py_ID(print_file_and_line), &tmp) < 0) {
+        if (_PyObject_LookupAttr(exc, &_Py_ID(print_file_and_line), &tmp) < 0) {
             _PyErr_Clear(tstate);
         }
         else if (tmp) {
             Py_DECREF(tmp);
         }
         else {
-            if (PyObject_SetAttr(v, &_Py_ID(print_file_and_line), Py_None)) {
+            if (PyObject_SetAttr(exc, &_Py_ID(print_file_and_line), Py_None)) {
                 _PyErr_Clear(tstate);
             }
         }
     }
-    _PyErr_Restore(tstate, exc, v, tb);
+    _PyErr_SetRaisedException(tstate, exc);
 }
 
 void