introduce tcmalloc::StaticStorage

We have a number of things that are explicitly constructed in some
statically allocated space, so lets finally have a helper for that.

src/base/static_storage.h

@@ -0,0 +1,61 @@
+/* -*- Mode: C++; c-basic-offset: 2; indent-tabs-mode: nil -*-
+ * Copyright (c) 2024, gperftools Contributors
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+#ifndef BASE_STATIC_STORAGE_H_
+#define BASE_STATIC_STORAGE_H_
+#include "config.h"
+
+#include <stdint.h>
+
+#include <utility>
+
+namespace tcmalloc {
+
+template <typename T>
+class StaticStorage {
+public:
+  T* get() {
+    return reinterpret_cast<T*>(bytes_);
+  }
+  const T* get() const {
+    return reinterpret_cast<const T*>(bytes_);
+  }
+
+  template <class... U>
+  T* Construct(U&&... u) {
+    return new (bytes_) T(std::forward<U>(u)...);
+  }
+private:
+  alignas(alignof(T)) uint8_t bytes_[sizeof(T)];
+};
+
+}  // namespace tcmalloc
+
+#endif  // BASE_STATIC_STORAGE_H_

src/emergency_malloc.cc

@@ -42,6 +42,7 @@
 #include "base/logging.h"
 #include "base/low_level_alloc.h"
 #include "base/spinlock.h"
+#include "base/static_storage.h"
 #include "internal_logging.h"
 #include "mmap_hook.h"
 #include "thread_cache_ptr.h"
@@ -80,11 +81,9 @@ static void InitEmergencyMalloc(void) {
 
   emergency_arena_end = emergency_arena_start = reinterpret_cast<char *>(ptr);
 
-  static struct alignas(alignof(EmergencyArenaPagesAllocator)) {
-    uint8_t bytes[sizeof(EmergencyArenaPagesAllocator)];
-  } pages_allocator_place;
+  static StaticStorage<EmergencyArenaPagesAllocator> pages_allocator_place;
+  EmergencyArenaPagesAllocator* allocator = pages_allocator_place.Construct();
 
-  EmergencyArenaPagesAllocator *allocator = new (&pages_allocator_place) EmergencyArenaPagesAllocator();
   emergency_arena = LowLevelAlloc::NewArenaWithCustomAlloc(0, LowLevelAlloc::DefaultArena(), allocator);
 
   emergency_arena_start_shifted = reinterpret_cast<uintptr_t>(emergency_arena_start) >> kEmergencyArenaShift;