🐛 Separate control from GCC & e-except

GCC needs more memory because it needs to allocate the exception
header for every exception.

Author: kammce

CMakeLists.txt

@@ -32,7 +32,6 @@ libhal_make_library(
   LIBRARY_NAME libhal-exceptions
 
   SOURCES
-  src/control.cpp
   ${SOURCE_LIST}
 
   PACKAGES
@@ -49,7 +48,6 @@ libhal_unit_test(
   LIBRARY_NAME libhal-exceptions
 
   SOURCES
-  src/control.cpp
   tests/main.test.cpp
   tests/control.test.cpp
   ${SOURCE_LIST}

src/arm_cortex/estell/exception.cpp

@@ -2139,3 +2139,85 @@ extern "C"
   }
 }  // extern "C"
 // NOLINTEND(bugprone-reserved-identifier)
+
+namespace __cxxabiv1 {                                // NOLINT
+std::terminate_handler __terminate_handler = +[]() {  // NOLINT
+  while (true) {
+    continue;
+  }
+};
+}  // namespace __cxxabiv1
+
+namespace hal {
+std::terminate_handler set_terminate(
+  std::terminate_handler p_terminate_handler) noexcept
+{
+  auto copy = __cxxabiv1::__terminate_handler;
+  __cxxabiv1::__terminate_handler = p_terminate_handler;
+  return copy;
+}
+
+std::terminate_handler get_terminate() noexcept
+{
+  return __cxxabiv1::__terminate_handler;
+}
+
+/**
+ * @brief Simple exception allocator
+ *
+ * This allocator can only allocates space for a single exception object at a
+ * time.
+ */
+class single_exception_allocator : public std::pmr::memory_resource
+{
+public:
+  single_exception_allocator() = default;
+  ~single_exception_allocator() override = default;
+
+private:
+  void* do_allocate(std::size_t p_size,  // NOLINT
+                    [[maybe_unused]] std::size_t p_alignment) override
+  {
+    if (m_allocated || p_size > m_buffer.size()) {
+      return nullptr;
+    }
+    m_allocated = true;
+    return m_buffer.data();
+  }
+
+  void do_deallocate(void* p_address,
+                     [[maybe_unused]] std::size_t p_size,  // NOLINT
+                     [[maybe_unused]] std::size_t p_alignment) override
+  {
+    if (p_address != m_buffer.data()) {
+      std::terminate();
+    }
+    m_allocated = false;
+  }
+
+  [[nodiscard]] bool do_is_equal(
+    std::pmr::memory_resource const& other) const noexcept override
+  {
+    return this == &other;
+  }
+
+  alignas(std::max_align_t) std::array<std::uint8_t, 64> m_buffer{};
+  bool m_allocated = false;
+};
+
+// TODO(#11): Add macro to IFDEF this out if the user want to save 64 bytes.
+// NOLINTNEXTLINE
+single_exception_allocator _default_allocator{};
+// NOLINTNEXTLINE
+std::pmr::memory_resource* _exception_allocator = &_default_allocator;
+
+void set_exception_allocator(std::pmr::memory_resource& p_allocator) noexcept
+{
+  _exception_allocator = &p_allocator;
+}
+
+std::pmr::memory_resource& get_exception_allocator() noexcept
+{
+  return *_exception_allocator;
+}
+}  // namespace hal

src/builtin/gcc/impl.cpp

@@ -16,44 +16,64 @@
 #include <cstdint>
 
 #include <algorithm>
+#include <array>
 #include <exception>
+#include <memory_resource>
 
 #include <libhal-exceptions/control.hpp>
 
+namespace {
+
+// Size of the GCC exception object header is 128 bytes. Will have to update
+// this if the size of the EO increases. 😅
+// Might need to add some GCC macro flags here to keep track of all of the
+// EO sizes over the versions.
+constexpr size_t gcc_header_size = 128;
+
+template<typename T = std::byte>
+struct exception_allocation
+{
+  std::size_t size;
+  std::array<std::byte, 256> header;
+  alignas(std::max_align_t) T data;
+};
+
+template<typename T = std::byte>
+exception_allocation<T>* get_allocation_from_exception(void* p_exception_ptr)
+{
+  auto const member_offset = offsetof(exception_allocation<T>, data);
+  auto const exception_bytes = static_cast<std::byte*>(p_exception_ptr);
+  return reinterpret_cast<exception_allocation<T>*>(exception_bytes -
+                                                    member_offset);
+}
+
+}  // namespace
+
 extern "C"
 {
   void _exit([[maybe_unused]] int rc)  // NOLINT
   {
     std::terminate();
   }
 
-  // Size of the GCC exception object header is 128 bytes. Will have to update
-  // this if the size of the EO increases. 😅
-  // Might need to add some GCC macro flags here to keep track of all of the
-  // EO sizes over the versions.
-  constexpr size_t gcc_header_size = 128;
-  constexpr auto header_size = sizeof(std::size_t) + gcc_header_size;
-
   void* __wrap___cxa_allocate_exception(std::size_t p_size) noexcept  // NOLINT
   {
-    auto const total_allocation = header_size + p_size;
-    auto* exception_memory = reinterpret_cast<std::uint8_t*>(
-      hal::get_exception_allocator().allocate(total_allocation));
 
-    if (exception_memory == nullptr) {
+    auto const allocation_amount = sizeof(exception_allocation<>) + p_size;
+    auto exception_memory_resource = &hal::get_exception_allocator();
+
+    auto* object = static_cast<exception_allocation<>*>(
+      exception_memory_resource->allocate(allocation_amount));
+
+    if (object == nullptr) {
       std::terminate();
     }
 
     // Required for GCC's impl to work correctly as it assumes that all bytes
     // default to 0.
-    std::fill_n(exception_memory, total_allocation, 0U);
-
-    // Set the first std::size_t bytes to the header size for deallocation
-    reinterpret_cast<std::size_t*>(exception_memory)[0] = total_allocation;
-
-    // Return the pointer to the memory after the header, which is the start of
-    // the thrown object's allocated memory.
-    return exception_memory + header_size;
+    object->header.fill(std::byte{ 0 });
+    object->size = allocation_amount;
+    return &object->data;
   }
 
   void __wrap___cxa_call_unexpected(void*)  // NOLINT
@@ -63,9 +83,89 @@ extern "C"
 
   void __wrap___cxa_free_exception(void* p_exception) noexcept  // NOLINT
   {
-    auto* exception = reinterpret_cast<std::uint8_t*>(p_exception);
-    auto* original_pointer = exception - header_size;
-    auto exception_size = *reinterpret_cast<std::size_t*>(original_pointer);
-    hal::get_exception_allocator().deallocate(original_pointer, exception_size);
+    auto* object = get_allocation_from_exception(p_exception);
+    hal::get_exception_allocator().deallocate(object, object->size);
   }
 }  // extern "C"
+
+namespace __cxxabiv1 {                                // NOLINT
+std::terminate_handler __terminate_handler = +[]() {  // NOLINT
+  while (true) {
+    continue;
+  }
+};
+}  // namespace __cxxabiv1
+
+namespace hal {
+std::terminate_handler set_terminate(
+  std::terminate_handler p_terminate_handler) noexcept
+{
+  auto copy = __cxxabiv1::__terminate_handler;
+  __cxxabiv1::__terminate_handler = p_terminate_handler;
+  return copy;
+}
+
+std::terminate_handler get_terminate() noexcept
+{
+  return __cxxabiv1::__terminate_handler;
+}
+
+/**
+ * @brief Simple exception allocator
+ *
+ * This allocator can only allocates space for a single exception object at a
+ * time.
+ */
+class single_exception_allocator : public std::pmr::memory_resource
+{
+public:
+  single_exception_allocator() = default;
+  ~single_exception_allocator() override = default;
+
+private:
+  void* do_allocate(std::size_t p_size,  // NOLINT
+                    [[maybe_unused]] std::size_t p_alignment) override
+  {
+    if (m_allocated || p_size > m_buffer.size()) {
+      return nullptr;
+    }
+    m_allocated = true;
+    return m_buffer.data();
+  }
+
+  void do_deallocate(void* p_address,
+                     [[maybe_unused]] std::size_t p_size,  // NOLINT
+                     [[maybe_unused]] std::size_t p_alignment) override
+  {
+    if (p_address != m_buffer.data()) {
+      std::terminate();
+    }
+    m_allocated = false;
+  }
+
+  [[nodiscard]] bool do_is_equal(
+    std::pmr::memory_resource const& other) const noexcept override
+  {
+    return this == &other;
+  }
+
+  alignas(std::max_align_t) std::array<std::uint8_t, 256> m_buffer{};
+  bool m_allocated = false;
+};
+
+// TODO(#11): Add macro to IFDEF this out if the user want to save 64 bytes.
+// NOLINTNEXTLINE
+single_exception_allocator _default_allocator{};
+// NOLINTNEXTLINE
+std::pmr::memory_resource* _exception_allocator = &_default_allocator;
+
+void set_exception_allocator(std::pmr::memory_resource& p_allocator) noexcept
+{
+  _exception_allocator = &p_allocator;
+}
+
+std::pmr::memory_resource& get_exception_allocator() noexcept
+{
+  return *_exception_allocator;
+}
+}  // namespace hal