Alias settings_client internals to see it in a memory dump.

chromium_src/base/debug/alias.h

@@ -0,0 +1,73 @@
+/* Copyright (c) 2024 The Brave Authors. All rights reserved.
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#ifndef BRAVE_CHROMIUM_SRC_BASE_DEBUG_ALIAS_H_
+#define BRAVE_CHROMIUM_SRC_BASE_DEBUG_ALIAS_H_
+
+#include "base/containers/span.h"
+#include "base/memory/raw_ptr_exclusion.h"
+#include "base/memory/stack_allocated.h"
+#include "base/ranges/algorithm.h"
+
+#include "src/base/debug/alias.h"  // IWYU pragma: export
+
+namespace base::debug {
+
+// StackObjectCopy creates a byte-for-byte copy of an object on the stack,
+// allowing the object to be inspected in crash dumps even if the original
+// object is optimized away by the compiler or is stored in protected memory.
+// The copy maintains proper alignment and can be viewed as the original type in
+// a debugger.
+template <typename T>
+class StackObjectCopy {
+  STACK_ALLOCATED();
+
+ public:
+  explicit StackObjectCopy(const T* original) {
+    if (original) {
+      // SAFETY: `original` is a valid pointer to a T object, and `kSize` is the
+      // size of T.
+      //
+      // Can't use `byte_span_from_ref` because `T` might be an abstract class.
+      auto original_object_memory = UNSAFE_BUFFERS(
+          make_span(reinterpret_cast<const uint8_t*>(original), kSize));
+      span(buffer_).copy_from(std::move(original_object_memory));
+    } else {
+      ranges::fill(buffer_, 0);
+    }
+  }
+
+  ~StackObjectCopy() {
+    // Ensure the class isn't optimized away before destruction.
+    Alias(buffer_);
+  }
+
+  StackObjectCopy(const StackObjectCopy&) = delete;
+  StackObjectCopy& operator=(const StackObjectCopy&) = delete;
+
+ private:
+  constexpr static size_t kSize = sizeof(T);
+  constexpr static size_t kMinSize = 128;
+
+  alignas(T) uint8_t buffer_[kSize];
+  RAW_PTR_EXCLUSION const T* const typed_view_ =
+      reinterpret_cast<const T*>(buffer_);
+  // Prevent the class from being optimized down to a register value.
+  const uint8_t padding_[kSize >= kMinSize ? 0 : kMinSize - kSize] = {};
+};
+
+}  // namespace base::debug
+
+// DEBUG_ALIAS_FOR_OBJECT creates a stack copy of an object and ensures it
+// remains in memory for crash dumps. This is useful when you need to ensure an
+// object's state is captured in crash reports, especially when the object might
+// otherwise be optimized away or is not directly accessible.
+//
+// Usage: DEBUG_ALIAS_FOR_OBJECT(alias_name, pointer_to_object);
+#define DEBUG_ALIAS_FOR_OBJECT(var_name, object)         \
+  const ::base::debug::StackObjectCopy var_name(object); \
+  ::base::debug::Alias(&var_name)
+
+#endif  // BRAVE_CHROMIUM_SRC_BASE_DEBUG_ALIAS_H_

chromium_src/check_chromium_src_config.json5

@@ -50,6 +50,9 @@
     // These symbols found in associated paths will be ignored.
     // Please, keep paths and symbols in alphabetical order.
     "symbol_excludes": {
+        "base/debug/alias.h": [
+            "DEBUG_ALIAS_FOR_OBJECT",
+        ],
         "base/trace_event/builtin_categories.h": [
             "BRAVE_INTERNAL_TRACE_LIST_BUILTIN_CATEGORIES",
         ],

third_party/blink/renderer/core/farbling/brave_session_cache.cc

@@ -144,7 +144,7 @@ blink::WebContentSettingsClient* GetContentSettingsClientFor(
     return worker_or_worklet->ContentSettingsClient();
   }
 
-  base::debug::Alias(context);
+  DEBUG_ALIAS_FOR_OBJECT(context_alias, context);
   NOTREACHED() << "Unhandled ExecutionContext type";
 }
 
@@ -446,9 +446,9 @@ BraveFarblingLevel BraveSessionCache::GetBraveFarblingLevel(
             GetContentSettingsClientFor(GetSupplementable())) {
       auto shields_settings =
           settings_client->GetBraveShieldsSettings(webcompat_content_settings);
-      // https://github.com/brave/brave-browser/issues/41724 debug.
+      // https://github.com/brave/brave-browser/issues/41889 debug.
       if (!shields_settings) {
-        base::debug::Alias(settings_client);
+        DEBUG_ALIAS_FOR_OBJECT(settings_client_alias, settings_client);
         base::debug::DumpWithoutCrashing();
         return default_shields_settings_->farbling_level;
       }