Fix too early writebarrier in tally_up

jhawthorn · jhawthorn · commit a7dc515c1df3 · 2025-06-17T15:32:53.000-07:00
After returning from the callback in st_update is the point that the
hash table may be resized, which could trigger a GC and mark the table
being used for the tally.

    RUBY_GC_LIBRARY=wbcheck WBCHECK_VERIFY_AFTER_WB=1 ./miniruby -e '(0...100).map(&amp;:to_s).tally'
diff --git a/enum.c b/enum.c
@@ -1215,14 +1215,15 @@ tally_up(st_data_t *group, st_data_t *value, st_data_t arg, int existing)
         RB_OBJ_WRITTEN(hash, Qundef, tally);
     }
     *value = (st_data_t)tally;
-    if (!SPECIAL_CONST_P(*group)) RB_OBJ_WRITTEN(hash, Qundef, *group);
     return ST_CONTINUE;
 }
 
 static VALUE
 rb_enum_tally_up(VALUE hash, VALUE group)
 {
-    rb_hash_stlike_update(hash, group, tally_up, (st_data_t)hash);
+    if (!rb_hash_stlike_update(hash, group, tally_up, (st_data_t)hash)) {
+        RB_OBJ_WRITTEN(hash, Qundef, group);
+    }
     return hash;
 }
 

Original file line number	Diff line number	Diff line change
`@@ -1215,14 +1215,15 @@ tally_up(st_data_t group, st_data_t value, st_data_t arg, int existing)`
`1215`	`1215`	`RB_OBJ_WRITTEN(hash, Qundef, tally);`
`1216`	`1216`	`}`
`1217`	`1217`	`*value = (st_data_t)tally;`
`1218`		`- if (!SPECIAL_CONST_P(group)) RB_OBJ_WRITTEN(hash, Qundef, group);`
`1219`	`1218`	`return ST_CONTINUE;`
`1220`	`1219`	`}`
`1221`	`1220`
`1222`	`1221`	`static VALUE`
`1223`	`1222`	`rb_enum_tally_up(VALUE hash, VALUE group)`
`1224`	`1223`	`{`
`1225`		`- rb_hash_stlike_update(hash, group, tally_up, (st_data_t)hash);`
	`1224`	`+ if (!rb_hash_stlike_update(hash, group, tally_up, (st_data_t)hash)) {`
	`1225`	`+ RB_OBJ_WRITTEN(hash, Qundef, group);`
	`1226`	`+ }`
`1226`	`1227`	`return hash;`
`1227`	`1228`	`}`
`1228`	`1229`