bpo-38379: don't claim objects are collected when they aren't (#16658)

* bpo-38379:  when a finalizer resurrects an object,
nothing is actually collected in this run of gc.
Change the stats to relect that truth.

1 files changed, 4 insertions, 6 deletions

diff --git a/Modules/gcmodule.c b/Modules/gcmodule.c
index 2b47abae1a..766f8e0c67 100644
--- a/Modules/gcmodule.c
+++ b/Modules/gcmodule.c
@@ -1095,12 +1095,9 @@ collect(struct _gc_runtime_state *state, int generation,
     validate_list(&finalizers, 0);
     validate_list(&unreachable, PREV_MASK_COLLECTING);
 
-    /* Collect statistics on collectable objects found and print
-     * debugging information.
-     */
-    for (gc = GC_NEXT(&unreachable); gc != &unreachable; gc = GC_NEXT(gc)) {
-        m++;
-        if (state->debug & DEBUG_COLLECTABLE) {
+    /* Print debugging information. */
+    if (state->debug & DEBUG_COLLECTABLE) {
+        for (gc = GC_NEXT(&unreachable); gc != &unreachable; gc = GC_NEXT(gc)) {
             debug_cycle("collectable", FROM_GC(gc));
         }
     }
@@ -1122,6 +1119,7 @@ collect(struct _gc_runtime_state *state, int generation,
          * the reference cycles to be broken.  It may also cause some objects
          * in finalizers to be freed.
          */
+        m += gc_list_size(&unreachable);
         delete_garbage(state, &unreachable, old);
     }