Static Allocator - Aligned allocations

osrf_testing_tools_cpp/src/memory_tools/impl/linux.cpp

@@ -42,13 +42,21 @@ find_original_function(const char * name)
   return original_function;
 }
 
+// An amount of memory that is greater than what is needed for static initialization
+// for any test we run. It was found experimentally on Ubuntu Linux 16.04 x86_64.
+static const size_t STATIC_ALLOCATOR_SIZE = 0x800000;
 using osrf_testing_tools_cpp::memory_tools::impl::StaticAllocator;
-// the size was found experimentally on Ubuntu Linux 16.04 x86_64
-using StaticAllocatorT = StaticAllocator<8388608>;
-// used to fullfil calloc call from dlerror.c during initialization of original functions
-// constructor is called on first use with a placement-new and the static storage
+using StaticAllocatorT = StaticAllocator<STATIC_ALLOCATOR_SIZE>;
 static uint8_t g_static_allocator_storage[sizeof(StaticAllocatorT)];
-static StaticAllocatorT * g_static_allocator = nullptr;
+
+// Contains global allocator to make 100% sure to avoid Static Initialization Order Fiasco.
+// "Construct on first use" idiom
+StaticAllocatorT * g_static_allocator() {
+  // placement-new the static allocator in preallocated storage
+  // which is used while finding the original memory functions
+  static StaticAllocatorT * alloc = new (g_static_allocator_storage) StaticAllocatorT;
+  return alloc;
+}
 
 // storage for original malloc/realloc/calloc/free
 using MallocSignature = void * (*)(size_t);
@@ -78,12 +86,7 @@ void *
 malloc(size_t size) noexcept
 {
   if (!get_static_initialization_complete()) {
-    if (nullptr == g_static_allocator) {
-      // placement-new the static allocator
-      // which is used while finding the original memory functions
-      g_static_allocator = new (g_static_allocator_storage) StaticAllocatorT;
-    }
-    return g_static_allocator->allocate(size);
+    return g_static_allocator()->allocate(size);
   }
   return unix_replacement_malloc(size, g_original_malloc);
 }
@@ -92,12 +95,7 @@ void *
 realloc(void * pointer, size_t size) noexcept
 {
   if (!get_static_initialization_complete()) {
-    if (nullptr == g_static_allocator) {
-      // placement-new the static allocator
-      // which is used while finding the original memory functions
-      g_static_allocator = new (g_static_allocator_storage) StaticAllocatorT;
-    }
-    return g_static_allocator->reallocate(pointer, size);
+    return g_static_allocator()->reallocate(pointer, size);
   }
   return unix_replacement_realloc(pointer, size, g_original_realloc);
 }
@@ -106,20 +104,15 @@ void *
 calloc(size_t count, size_t size) noexcept
 {
   if (!get_static_initialization_complete()) {
-    if (nullptr == g_static_allocator) {
-      // placement-new the static allocator
-      // which is used while finding the original memory functions
-      g_static_allocator = new (g_static_allocator_storage) StaticAllocatorT;
-    }
-    return g_static_allocator->zero_allocate(count, size);
+    return g_static_allocator()->zero_allocate(count, size);
   }
   return unix_replacement_calloc(count, size, g_original_calloc);
 }
 
 void
 free(void * pointer) noexcept
 {
-  if (nullptr == pointer || g_static_allocator->deallocate(pointer)) {
+  if (nullptr == pointer || g_static_allocator()->deallocate(pointer)) {
     // free of nullptr or,
     // memory was originally allocated by static allocator, no need to pass to "real" free
     return;

osrf_testing_tools_cpp/src/memory_tools/impl/static_allocator.hpp

@@ -45,9 +45,10 @@ class StaticAllocator
   void *
   allocate(size_t size)
   {
-    if (size <= size_t(std::distance(stack_pointer_, end_))) {
+    auto const aligned_size = align_up(size);
+    if (aligned_size <= static_cast<decltype(aligned_size)>(std::distance(end_, stack_pointer_))) {
       uint8_t * result = stack_pointer_;
-      stack_pointer_ += size;
+      stack_pointer_ += aligned_size;
       return result;
     }
     SAFE_FWRITE(stderr, "StackAllocator.allocate() -> nullptr\n");
@@ -105,7 +106,14 @@ class StaticAllocator
   }
 
 private:
-  uint8_t memory_pool_[MemoryPoolSize];
+  static std::size_t
+  align_up(std::size_t n) noexcept
+  {
+    return (n+(alignment-1)) & ~(alignment-1);
+  }
+
+  static auto constexpr alignment = alignof(std::max_align_t);
+  alignas(alignment) uint8_t memory_pool_[MemoryPoolSize];
   uint8_t * begin_;
   uint8_t * end_;
   uint8_t * stack_pointer_;
@@ -115,12 +123,4 @@ class StaticAllocator
 }  // namespace memory_tools
 }  // namespace osrf_testing_tools_cpp
 
-int main(void)
-{
-  osrf_testing_tools_cpp::memory_tools::impl::StaticAllocator<64> sa;
-  void * mem = sa.allocate(16);
-  (void)mem;
-  return 0;
-}
-
 #endif  // MEMORY_TOOLS__IMPL__STATIC_ALLOCATOR_HPP_