Start with mark phase

Author: markshannon

Include/internal/pycore_gc.h

@@ -303,9 +303,8 @@ struct gc_generation_stats {
 };
 
 enum _GCPhase {
-    GC_PHASE_DONE = 0,
-    GC_PHASE_MARK = 1,
-    GC_PHASE_COLLECT = 2
+    GC_PHASE_MARK = 0,
+    GC_PHASE_COLLECT = 1
 };
 
 struct _gc_runtime_state {

Include/internal/pycore_runtime_init.h

@@ -132,6 +132,7 @@ extern PyTypeObject _PyExc_MemoryError;
                 { .threshold = 0, }, \
             }, \
             .work_to_do = -5000, \
+            .phase = 0, \
         }, \
         .qsbr = { \
             .wr_seq = QSBR_INITIAL, \