bpo-41117: Cleanup subtract_refs() (GH-27593)

vstinner · web-flow · commit c34fa2bb06ea · 2021-08-04T18:09:14.000+02:00
subtract_refs() reuses the 'op' variable rather than calling the
FROM_GC() macro twice.

Issue reported by William Pickard.
diff --git a/Modules/gcmodule.c b/Modules/gcmodule.c
@@ -479,9 +479,9 @@ subtract_refs(PyGC_Head *containers)
     for (; gc != containers; gc = GC_NEXT(gc)) {
         PyObject *op = FROM_GC(gc);
         traverse = Py_TYPE(op)->tp_traverse;
-        (void) traverse(FROM_GC(gc),
-                       (visitproc)visit_decref,
-                       op);
+        (void) traverse(op,
+                        (visitproc)visit_decref,
+                        op);
     }
 }
 

Original file line number	Diff line number	Diff line change
`@@ -479,9 +479,9 @@ subtract_refs(PyGC_Head *containers)`
`479`	`479`	`for (; gc != containers; gc = GC_NEXT(gc)) {`
`480`	`480`	`PyObject *op = FROM_GC(gc);`
`481`	`481`	`traverse = Py_TYPE(op)->tp_traverse;`
`482`		`- (void) traverse(FROM_GC(gc),`
`483`		`- (visitproc)visit_decref,`
`484`		`- op);`
	`482`	`+ (void) traverse(op,`
	`483`	`+ (visitproc)visit_decref,`
	`484`	`+ op);`
`485`	`485`	`}`
`486`	`486`	`}`
`487`	`487`