bpo-38631: Avoid Py_FatalError() in GC collect() (GH-18164)

vstinner · web-flow · commit 656c45ec9a9d · 2020-01-24T18:05:24.000+01:00
collect() should not get an exception, but it does, logging the
exception is enough. Override sys.unraisablehook to decide how to
handle unraisable exceptions.

Py_FatalError() should be avoided whenever possible.
diff --git a/Modules/gcmodule.c b/Modules/gcmodule.c
@@ -118,9 +118,6 @@ gc_decref(PyGC_Head *g)
     g->_gc_prev -= 1 << _PyGC_PREV_SHIFT;
 }
 
-/* Python string to use if unhandled exception occurs */
-static PyObject *gc_str = NULL;
-
 /* set for debugging information */
 #define DEBUG_STATS             (1<<0) /* print collection statistics */
 #define DEBUG_COLLECTABLE       (1<<1) /* print collectable objects */
@@ -1310,10 +1307,7 @@ collect(PyThreadState *tstate, int generation,
             _PyErr_Clear(tstate);
         }
         else {
-            if (gc_str == NULL)
-                gc_str = PyUnicode_FromString("garbage collection");
-            PyErr_WriteUnraisable(gc_str);
-            Py_FatalError("unexpected exception during garbage collection");
+            _PyErr_WriteUnraisableMsg("in garbage collection", NULL);
         }
     }
 

Original file line number	Diff line number	Diff line change
`@@ -118,9 +118,6 @@ gc_decref(PyGC_Head *g)`
`118`	`118`	`g->_gc_prev -= 1 << _PyGC_PREV_SHIFT;`
`119`	`119`	`}`
`120`	`120`
`121`		`-/* Python string to use if unhandled exception occurs */`
`122`		`-static PyObject *gc_str = NULL;`
`123`		`-`
`124`	`121`	`/* set for debugging information */`
`125`	`122`	`#define DEBUG_STATS (1<<0) /* print collection statistics */`
`126`	`123`	`#define DEBUG_COLLECTABLE (1<<1) /* print collectable objects */`
`@@ -1310,10 +1307,7 @@ collect(PyThreadState *tstate, int generation,`
`1310`	`1307`	`_PyErr_Clear(tstate);`
`1311`	`1308`	`}`
`1312`	`1309`	`else {`
`1313`		`- if (gc_str == NULL)`
`1314`		`- gc_str = PyUnicode_FromString("garbage collection");`
`1315`		`- PyErr_WriteUnraisable(gc_str);`
`1316`		`- Py_FatalError("unexpected exception during garbage collection");`
	`1310`	`+ _PyErr_WriteUnraisableMsg("in garbage collection", NULL);`
`1317`	`1311`	`}`
`1318`	`1312`	`}`
`1319`	`1313`