[Bug #21620] Fix strict aliasing in rb_managed_id_table_lookup

We cannot pass &ccs into rb_managed_id_table_lookup because rb_managed_id_table_lookup
takes in a VALUE*, so it violates strict aliasing in C. This causes segfaults
when compiling with LTO enabled.

Author: peterzhu2118

vm_insnhelper.c

@@ -2120,8 +2120,9 @@ vm_evict_cc(VALUE klass, VALUE cc_tbl, ID mid)
             return;
         }
 
-        struct rb_class_cc_entries *ccs = NULL;
-        rb_managed_id_table_lookup(cc_tbl, mid, (VALUE *)&ccs);
+        VALUE ccs_obj = 0;
+        rb_managed_id_table_lookup(cc_tbl, mid, &ccs_obj);
+        struct rb_class_cc_entries *ccs = (struct rb_class_cc_entries *)ccs_obj;
 
         if (!ccs || !METHOD_ENTRY_INVALIDATED(ccs->cme)) {
             // Another ractor replaced that entry while we were waiting on the VM lock.
@@ -2182,7 +2183,11 @@ vm_populate_cc(VALUE klass, const struct rb_callinfo * const ci, ID mid)
     if (ccs == NULL) {
         VM_ASSERT(cc_tbl);
 
-        if (!LIKELY(rb_managed_id_table_lookup(cc_tbl, mid, (VALUE *)&ccs))) {
+        VALUE ccs_obj;
+        if (UNLIKELY(rb_managed_id_table_lookup(cc_tbl, mid, &ccs_obj))) {
+            ccs = (struct rb_class_cc_entries *)ccs_obj;
+        }
+        else {
             // TODO: required?
             ccs = vm_ccs_create(klass, cc_tbl, mid, cme);
         }
@@ -2217,7 +2222,9 @@ vm_lookup_cc(const VALUE klass, const struct rb_callinfo * const ci, ID mid)
         // CCS data is keyed on method id, so we don't need the method id
         // for doing comparisons in the `for` loop below.
 
-        if (rb_managed_id_table_lookup(cc_tbl, mid, (VALUE *)&ccs)) {
+        VALUE ccs_obj;
+        if (rb_managed_id_table_lookup(cc_tbl, mid, &ccs_obj)) {
+            ccs = (struct rb_class_cc_entries *)ccs_obj;
             const int ccs_len = ccs->len;
 
             if (UNLIKELY(METHOD_ENTRY_INVALIDATED(ccs->cme))) {

vm_method.c

@@ -195,8 +195,9 @@ rb_vm_ccs_invalidate_and_free(struct rb_class_cc_entries *ccs)
 void
 rb_vm_cc_table_delete(VALUE table, ID mid)
 {
-    struct rb_class_cc_entries *ccs;
-    if (rb_managed_id_table_lookup(table, mid, (VALUE *)&ccs)) {
+    VALUE ccs_obj;
+    if (rb_managed_id_table_lookup(table, mid, &ccs_obj)) {
+        struct rb_class_cc_entries *ccs = (struct rb_class_cc_entries *)ccs_obj;
         rb_managed_id_table_delete(table, mid);
         rb_vm_ccs_invalidate_and_free(ccs);
     }