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diff --git a/pw_tokenizer/size_report/base.h b/pw_tokenizer/size_report/base.h
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+++ b/pw_tokenizer/size_report/base.h
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+// Copyright 2022 The Pigweed Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may not
+// use this file except in compliance with the License. You may obtain a copy of
+// the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+// License for the specific language governing permissions and limitations under
+// the License.
+#pragma once
+
+#include "pw_tokenizer/tokenize.h"
+
+//
+// Baseline data container structure.
+//
+// This structure is a container for data used to establish a baseline for size
+// report diffs.
+//
+// The baseline contains one global instance of this structure. Other binaries
+// should contain one global instance of a subclass of this structure, adding
+// any data that should be a part of the size report diff.
+//
+// This structure may be used to load sections of code and data in order to
+// establish a basline for size report diffs. This structure causes sections to
+// be loaded by referencing symbols within those sections.
+//
+// Simple references to symbols can be optimized out if they don't have any
+// external effects. The LoadData method uses functions and other symbols to
+// generate and return a run-time value. In this way, the symbol references
+// cannot be optimized out.
+//
+struct BaseContainer {
+  // Causes code and data sections to be loaded. Returns a generated value
+  // based on symbols in those sections to force them to be loaded. The caller
+  // should ensure that the return value has some external effect (e.g.,
+  // returning the value from the "main" function).
+  virtual long LoadData() {
+    // Prevent this object and token from being optimized out.
+    return reinterpret_cast<long>(this) ^ base_token;
+  }
+
+  // Destructor.
+  virtual ~BaseContainer() {}
+
+  // Reference the tokenizer.
+  uint32_t base_token = PW_TOKENIZE_STRING("base_token");
+
+  // Explicit padding. If this structure is empty, the baseline will include
+  // padding that won't appear in subclasses, so the padding is explicitly
+  // added here so it appears in both the baseline and all subclasses.
+  char padding[4];
+};