cppgc: Avoid using members on stack in cppgc

Bug: chromium:1283720
Cq-Include-Trybots: luci.v8.try:v8_linux_blink_rel
Change-Id: Ifd9982a9315ebbed8765bc9f15ac3ffcbf04612f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3368269
Auto-Submit: Omer Katz <omerkatz@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/main@{#78506}

include/cppgc/persistent.h

@@ -118,9 +118,9 @@ class BasicPersistent final : public PersistentBase,
   template <typename U, typename MemberBarrierPolicy,
             typename MemberWeaknessTag, typename MemberCheckingPolicy,
             typename = std::enable_if_t<std::is_base_of<T, U>::value>>
-  BasicPersistent(internal::BasicMember<U, MemberBarrierPolicy,
-                                        MemberWeaknessTag, MemberCheckingPolicy>
-                      member,
+  BasicPersistent(
+      const internal::BasicMember<U, MemberBarrierPolicy, MemberWeaknessTag,
+                                  MemberCheckingPolicy>& member,
       const SourceLocation& loc = SourceLocation::Current())
       : BasicPersistent(member.Get(), loc) {}
 
@@ -159,9 +159,8 @@ class BasicPersistent final : public PersistentBase,
             typename MemberWeaknessTag, typename MemberCheckingPolicy,
             typename = std::enable_if_t<std::is_base_of<T, U>::value>>
   BasicPersistent& operator=(
-      internal::BasicMember<U, MemberBarrierPolicy, MemberWeaknessTag,
-                            MemberCheckingPolicy>
-          member) {
+      const internal::BasicMember<U, MemberBarrierPolicy, MemberWeaknessTag,
+                                  MemberCheckingPolicy>& member) {
     return operator=(member.Get());
   }
 
@@ -292,12 +291,12 @@ template <typename T1, typename PersistentWeaknessPolicy,
           typename PersistentLocationPolicy, typename PersistentCheckingPolicy,
           typename T2, typename MemberWriteBarrierPolicy,
           typename MemberWeaknessTag, typename MemberCheckingPolicy>
-bool operator==(const BasicPersistent<T1, PersistentWeaknessPolicy,
-                                      PersistentLocationPolicy,
-                                      PersistentCheckingPolicy>& p,
-                BasicMember<T2, MemberWeaknessTag, MemberWriteBarrierPolicy,
-                            MemberCheckingPolicy>
-                    m) {
+bool operator==(
+    const BasicPersistent<T1, PersistentWeaknessPolicy,
+                          PersistentLocationPolicy, PersistentCheckingPolicy>&
+        p,
+    const BasicMember<T2, MemberWeaknessTag, MemberWriteBarrierPolicy,
+                      MemberCheckingPolicy>& m) {
   return p.Get() == m.Get();
 }
 
@@ -305,12 +304,12 @@ template <typename T1, typename PersistentWeaknessPolicy,
           typename PersistentLocationPolicy, typename PersistentCheckingPolicy,
           typename T2, typename MemberWriteBarrierPolicy,
           typename MemberWeaknessTag, typename MemberCheckingPolicy>
-bool operator!=(const BasicPersistent<T1, PersistentWeaknessPolicy,
-                                      PersistentLocationPolicy,
-                                      PersistentCheckingPolicy>& p,
-                BasicMember<T2, MemberWeaknessTag, MemberWriteBarrierPolicy,
-                            MemberCheckingPolicy>
-                    m) {
+bool operator!=(
+    const BasicPersistent<T1, PersistentWeaknessPolicy,
+                          PersistentLocationPolicy, PersistentCheckingPolicy>&
+        p,
+    const BasicMember<T2, MemberWeaknessTag, MemberWriteBarrierPolicy,
+                      MemberCheckingPolicy>& m) {
   return !(p == m);
 }
 
@@ -318,12 +317,12 @@ template <typename T1, typename MemberWriteBarrierPolicy,
           typename MemberWeaknessTag, typename MemberCheckingPolicy,
           typename T2, typename PersistentWeaknessPolicy,
           typename PersistentLocationPolicy, typename PersistentCheckingPolicy>
-bool operator==(BasicMember<T2, MemberWeaknessTag, MemberWriteBarrierPolicy,
-                            MemberCheckingPolicy>
-                    m,
+bool operator==(
+    const BasicMember<T2, MemberWeaknessTag, MemberWriteBarrierPolicy,
+                      MemberCheckingPolicy>& m,
     const BasicPersistent<T1, PersistentWeaknessPolicy,
-                                      PersistentLocationPolicy,
-                                      PersistentCheckingPolicy>& p) {
+                          PersistentLocationPolicy, PersistentCheckingPolicy>&
+        p) {
   return m.Get() == p.Get();
 }
 
@@ -331,12 +330,12 @@ template <typename T1, typename MemberWriteBarrierPolicy,
           typename MemberWeaknessTag, typename MemberCheckingPolicy,
           typename T2, typename PersistentWeaknessPolicy,
           typename PersistentLocationPolicy, typename PersistentCheckingPolicy>
-bool operator!=(BasicMember<T2, MemberWeaknessTag, MemberWriteBarrierPolicy,
-                            MemberCheckingPolicy>
-                    m,
+bool operator!=(
+    const BasicMember<T2, MemberWeaknessTag, MemberWriteBarrierPolicy,
+                      MemberCheckingPolicy>& m,
     const BasicPersistent<T1, PersistentWeaknessPolicy,
-                                      PersistentLocationPolicy,
-                                      PersistentCheckingPolicy>& p) {
+                          PersistentLocationPolicy, PersistentCheckingPolicy>&
+        p) {
   return !(m == p);
 }