symbol.c: use rb_gc_mark_and_move over rb_gc_location

byroot · byroot · commit 1986d775cdae · 2025-08-07T21:00:00.000+02:00
The `p-&gt;field = rb_gc_location(p-&gt;field)` isn't ideal because it means all
references are rewritten on compaction, regardless of whether the referenced
object has moved. This isn't good for caches nor for Copy-on-Write.

`rb_gc_mark_and_move` avoid needless writes, and most of the time allow to
have a single function for both marking and updating references.
diff --git a/gc.c b/gc.c
@@ -3028,7 +3028,7 @@ rb_gc_mark_roots(void *objspace, const char **categoryp)
     mark_current_machine_context(ec);
 
     MARK_CHECKPOINT("global_symbols");
-    rb_sym_global_symbols_mark();
+    rb_sym_global_symbols_mark_and_move();
 
     MARK_CHECKPOINT("finish");
 
@@ -4045,7 +4045,7 @@ rb_gc_update_vm_references(void *objspace)
 
     rb_vm_update_references(vm);
     rb_gc_update_global_tbl();
-    rb_sym_global_symbols_update_references();
+    rb_sym_global_symbols_mark_and_move();
 
 #if USE_YJIT
     void rb_yjit_root_update_references(void); // in Rust
diff --git a/internal/symbol.h b/internal/symbol.h
@@ -17,8 +17,7 @@
 #endif
 
 /* symbol.c */
-void rb_sym_global_symbols_mark(void);
-void rb_sym_global_symbols_update_references(void);
+void rb_sym_global_symbols_mark_and_move(void);
 VALUE rb_to_symbol_type(VALUE obj);
 VALUE rb_sym_intern(const char *ptr, long len, rb_encoding *enc);
 VALUE rb_sym_intern_ascii(const char *ptr, long len);
diff --git a/symbol.c b/symbol.c
@@ -371,21 +371,12 @@ Init_sym(void)
 }
 
 void
-rb_sym_global_symbols_mark(void)
+rb_sym_global_symbols_mark_and_move(void)
 {
     rb_symbols_t *symbols = &ruby_global_symbols;
 
-    rb_gc_mark_movable(symbols->sym_set);
-    rb_gc_mark_movable(symbols->ids);
-}
-
-void
-rb_sym_global_symbols_update_references(void)
-{
-    rb_symbols_t *symbols = &ruby_global_symbols;
-
-    symbols->sym_set = rb_gc_location(symbols->sym_set);
-    symbols->ids = rb_gc_location(symbols->ids);
+    rb_gc_mark_and_move(&symbols->sym_set);
+    rb_gc_mark_and_move(&symbols->ids);
 }
 
 static int
