Revert "Revert "Fix cvar caching when class is cloned""

This reverts commit 10621f7cb9a0c70e568f89cce47a02e878af6778. This was reverted because the gc integrity build started failing. We have figured out a fix so I'm reopening the PR. Original commit message: Fix cvar caching when class is cloned The class variable cache that was added in ruby#4544 changed the behavior of class variables on cloned classes. As reported when a class is cloned AND a class variable was set, and the class variable was read from the original class, reading a class variable from the cloned class would return the value from the original class. This was happening because the IC (inline cache) is stored on the ISEQ which is shared between the original and cloned class, therefore they share the cache too. To fix this we are now storing the `cref` in the cache so that we can check if it's equal to the current `cref`. If it's different we don't want to read from the cache. If it's the same we do. Cloned classes don't share the same cref with their original class. This will need to be backported to 3.1 in addition to 3.2 since the bug exists in both versions. We also added a marking function which was missing. Fixes [Bug #19379] Co-authored-by: Aaron Patterson <[email protected]>
author: eileencodes <[email protected]> 2023-06-02 14:25:19 -0400
committer: Aaron Patterson <[email protected]> 2023-06-05 11:11:12 -0700
commit: 40f090f4339820d19da8ecdf81a981489c22eb57 (patch)
tree: ee8f90b5d49c2bb6cc44f135e3638fcd9599722e
parent: 29ea3c5aaa9513fcd497781e7051c0f436725eb3 (diff)
8 files changed, 69 insertions, 8 deletions
diff --git a/class.c b/class.c
index 114df2bbd7..4ffb47c27a 100644
--- a/class.c
+++ b/class.c
@@ -446,9 +446,12 @@ cvc_table_copy(ID id, VALUE val, void *data)
 
     ent = ALLOC(struct rb_cvar_class_tbl_entry);
     ent->class_value = ctx->clone;
+    ent->cref = orig_entry->cref;
     ent->global_cvar_state = orig_entry->global_cvar_state;
     rb_id_table_insert(ctx->new_table, id, (VALUE)ent);
 
+    RB_OBJ_WRITTEN(ctx->clone, Qundef, ent->cref);
+
     return ID_TABLE_CONTINUE;
 }
 
diff --git a/ext/objspace/depend b/ext/objspace/depend
index 91ae569d67..d1e8236eb8 100644
--- a/ext/objspace/depend
+++ b/ext/objspace/depend
@@ -365,6 +365,11 @@ objspace.o: $(top_srcdir)/ccan/container_of/container_of.h
 objspace.o: $(top_srcdir)/ccan/list/list.h
 objspace.o: $(top_srcdir)/ccan/str/str.h
 objspace.o: $(top_srcdir)/constant.h
+objspace.o: $(hdrdir)/ruby/thread_native.h
+objspace.o: $(top_srcdir)/ccan/check_type/check_type.h
+objspace.o: $(top_srcdir)/ccan/container_of/container_of.h
+objspace.o: $(top_srcdir)/ccan/list/list.h
+objspace.o: $(top_srcdir)/ccan/str/str.h
 objspace.o: $(top_srcdir)/id_table.h
 objspace.o: $(top_srcdir)/internal.h
 objspace.o: $(top_srcdir)/internal/array.h
diff --git a/gc.c b/gc.c
index 44336c0d71..707754a9e5 100644
--- a/gc.c
+++ b/gc.c
@@ -7138,6 +7138,8 @@ gc_ref_update_from_offset(rb_objspace_t *objspace, VALUE obj)
     }
 }
 
+static void mark_cvc_tbl(rb_objspace_t *objspace, VALUE klass);
+
 static void
 gc_mark_children(rb_objspace_t *objspace, VALUE obj)
 {
@@ -7188,6 +7190,7 @@ gc_mark_children(rb_objspace_t *objspace, VALUE obj)
         if (!RCLASS_EXT(obj)) break;
 
         mark_m_tbl(objspace, RCLASS_M_TBL(obj));
+        mark_cvc_tbl(objspace, obj);
         cc_table_mark(objspace, obj);
         for (attr_index_t i = 0; i < RCLASS_IV_COUNT(obj); i++) {
             gc_mark(objspace, RCLASS_IVPTR(obj)[i]);
@@ -10325,9 +10328,14 @@ static enum rb_id_table_iterator_result
 update_cvc_tbl_i(VALUE cvc_entry, void *data)
 {
     struct rb_cvar_class_tbl_entry *entry;
+    rb_objspace_t * objspace = (rb_objspace_t *)data;
 
     entry = (struct rb_cvar_class_tbl_entry *)cvc_entry;
 
+    if (entry->cref) {
+        TYPED_UPDATE_IF_MOVED(objspace, rb_cref_t *, entry->cref);
+    }
+
     entry->class_value = rb_gc_location(entry->class_value);
 
     return ID_TABLE_CONTINUE;
@@ -10343,6 +10351,28 @@ update_cvc_tbl(rb_objspace_t *objspace, VALUE klass)
 }
 
 static enum rb_id_table_iterator_result
+mark_cvc_tbl_i(VALUE cvc_entry, void *data)
+{
+    struct rb_cvar_class_tbl_entry *entry;
+
+    entry = (struct rb_cvar_class_tbl_entry *)cvc_entry;
+
+    RUBY_ASSERT(entry->cref == 0 || (BUILTIN_TYPE((VALUE)entry->cref) == T_IMEMO && IMEMO_TYPE_P(entry->cref, imemo_cref)));
+    rb_gc_mark((VALUE) entry->cref);
+
+    return ID_TABLE_CONTINUE;
+}
+
+static void
+mark_cvc_tbl(rb_objspace_t *objspace, VALUE klass)
+{
+    struct rb_id_table *tbl = RCLASS_CVC_TBL(klass);
+    if (tbl) {
+        rb_id_table_foreach_values(tbl, mark_cvc_tbl_i, objspace);
+    }
+}
+
+static enum rb_id_table_iterator_result
 update_const_table(VALUE value, void *data)
 {
     rb_const_entry_t *ce = (rb_const_entry_t *)value;
diff --git a/internal/class.h b/internal/class.h
index b33c807e97..d76da84bd1 100644
--- a/internal/class.h
+++ b/internal/class.h
@@ -17,6 +17,9 @@
 #include "ruby/intern.h"        /* for rb_alloc_func_t */
 #include "ruby/ruby.h"          /* for struct RBasic */
 #include "shape.h"
+#include "ruby_assert.h"
+#include "vm_core.h"
+#include "method.h"             /* for rb_cref_t */
 
 #ifdef RCLASS_SUPER
 # undef RCLASS_SUPER
@@ -32,6 +35,7 @@ typedef struct rb_subclass_entry rb_subclass_entry_t;
 struct rb_cvar_class_tbl_entry {
     uint32_t index;
     rb_serial_t global_cvar_state;
+    const rb_cref_t * cref;
     VALUE class_value;
 };
 
diff --git a/test/ruby/test_variable.rb b/test/ruby/test_variable.rb
index 1158313776..e50b681ce8 100644
--- a/test/ruby/test_variable.rb
+++ b/test/ruby/test_variable.rb
@@ -49,6 +49,19 @@ class TestVariable < Test::Unit::TestCase
     assert_equal(1, c.class_variable_get(:@@foo))
   end
 
+  Zeus = Gods.clone
+
+  def test_cloned_allows_setting_cvar
+    Zeus.class_variable_set(:@@rule, "Athena")
+
+    god = Gods.new.ruler0
+    zeus = Zeus.new.ruler0
+
+    assert_equal "Cronus", god
+    assert_equal "Athena", zeus
+    assert_not_equal god.object_id, zeus.object_id
+  end
+
   def test_singleton_class_included_class_variable
     c = Class.new
     c.extend(Olympians)
diff --git a/variable.c b/variable.c
index 64cb07407c..0491562d22 100644
--- a/variable.c
+++ b/variable.c
@@ -3693,6 +3693,7 @@ rb_cvar_set(VALUE klass, ID id, VALUE val)
         ent = ALLOC(struct rb_cvar_class_tbl_entry);
         ent->class_value = target;
         ent->global_cvar_state = GET_GLOBAL_CVAR_STATE();
+        ent->cref = 0;
         rb_id_table_insert(rb_cvc_tbl, id, (VALUE)ent);
         RB_DEBUG_COUNTER_INC(cvar_inline_miss);
     }
diff --git a/vm_insnhelper.c b/vm_insnhelper.c
index 9407a75981..5ef1ad10de 100644
--- a/vm_insnhelper.c
+++ b/vm_insnhelper.c
@@ -1491,7 +1491,7 @@ vm_setivar(VALUE obj, ID id, VALUE val, shape_id_t dest_shape_id, attr_index_t i
 }
 
 static VALUE
-update_classvariable_cache(const rb_iseq_t *iseq, VALUE klass, ID id, ICVARC ic)
+update_classvariable_cache(const rb_iseq_t *iseq, VALUE klass, ID id, const rb_cref_t * cref, ICVARC ic)
 {
     VALUE defined_class = 0;
     VALUE cvar_value = rb_cvar_find(klass, id, &defined_class);
@@ -1511,9 +1511,13 @@ update_classvariable_cache(const rb_iseq_t *iseq, VALUE klass, ID id, ICVARC ic)
     }
 
     struct rb_cvar_class_tbl_entry *ent = (void *)ent_data;
-    ent->global_cvar_state = GET_GLOBAL_CVAR_STATE();
 
+    ent->global_cvar_state = GET_GLOBAL_CVAR_STATE();
+    ent->cref = cref;
     ic->entry = ent;
+
+    RUBY_ASSERT(BUILTIN_TYPE((VALUE)cref) == T_IMEMO && IMEMO_TYPE_P(cref, imemo_cref));
+    RB_OBJ_WRITTEN(iseq, Qundef, ent->cref);
     RB_OBJ_WRITTEN(iseq, Qundef, ent->class_value);
 
     return cvar_value;
@@ -1523,8 +1527,9 @@ static inline VALUE
 vm_getclassvariable(const rb_iseq_t *iseq, const rb_control_frame_t *reg_cfp, ID id, ICVARC ic)
 {
     const rb_cref_t *cref;
+    cref = vm_get_cref(GET_EP());
 
-    if (ic->entry && ic->entry->global_cvar_state == GET_GLOBAL_CVAR_STATE() && LIKELY(rb_ractor_main_p())) {
+    if (ic->entry && ic->entry->global_cvar_state == GET_GLOBAL_CVAR_STATE() && ic->entry->cref == cref && LIKELY(rb_ractor_main_p())) {
         RB_DEBUG_COUNTER_INC(cvar_read_inline_hit);
 
         VALUE v = rb_ivar_lookup(ic->entry->class_value, id, Qundef);
@@ -1533,10 +1538,9 @@ vm_getclassvariable(const rb_iseq_t *iseq, const rb_control_frame_t *reg_cfp, ID
         return v;
     }
 
-    cref = vm_get_cref(GET_EP());
     VALUE klass = vm_get_cvar_base(cref, reg_cfp, 1);
 
-    return update_classvariable_cache(iseq, klass, id, ic);
+    return update_classvariable_cache(iseq, klass, id, cref, ic);
 }
 
 VALUE
@@ -1549,20 +1553,20 @@ static inline void
 vm_setclassvariable(const rb_iseq_t *iseq, const rb_control_frame_t *reg_cfp, ID id, VALUE val, ICVARC ic)
 {
     const rb_cref_t *cref;
+    cref = vm_get_cref(GET_EP());
 
-    if (ic->entry && ic->entry->global_cvar_state == GET_GLOBAL_CVAR_STATE()) {
+    if (ic->entry && ic->entry->global_cvar_state == GET_GLOBAL_CVAR_STATE() && ic->entry->cref == cref && LIKELY(rb_ractor_main_p())) {
         RB_DEBUG_COUNTER_INC(cvar_write_inline_hit);
 
         rb_class_ivar_set(ic->entry->class_value, id, val);
         return;
     }
 
-    cref = vm_get_cref(GET_EP());
     VALUE klass = vm_get_cvar_base(cref, reg_cfp, 1);
 
     rb_cvar_set(klass, id, val);
 
-    update_classvariable_cache(iseq, klass, id, ic);
+    update_classvariable_cache(iseq, klass, id, cref, ic);
 }
 
 void
diff --git a/yjit/src/cruby_bindings.inc.rs b/yjit/src/cruby_bindings.inc.rs
index 048da7b0ff..16bb6e1feb 100644
--- a/yjit/src/cruby_bindings.inc.rs
+++ b/yjit/src/cruby_bindings.inc.rs
@@ -806,6 +806,7 @@ pub type rb_shape_t = rb_shape;
 pub struct rb_cvar_class_tbl_entry {
     pub index: u32,
     pub global_cvar_state: rb_serial_t,
+    pub cref: *const rb_cref_t,
     pub class_value: VALUE,
 }
 pub const VM_CALL_ARGS_SPLAT_bit: vm_call_flag_bits = 0;
author	eileencodes <[email protected]>	2023-06-02 14:25:19 -0400
committer	Aaron Patterson <[email protected]>	2023-06-05 11:11:12 -0700
commit	40f090f4339820d19da8ecdf81a981489c22eb57 (patch)
tree	ee8f90b5d49c2bb6cc44f135e3638fcd9599722e
parent	29ea3c5aaa9513fcd497781e7051c0f436725eb3 (diff)