Everywhere: Fix some alignment issues

When creating uninitialized storage for variables, we need to make sure
that the alignment is correct. Fixes a KUBSAN failure when running
kernels compiled with Clang.

In `Syscalls/socket.cpp`, we can simply use local variables, as
`sockaddr_un` is a POD type.

Along with moving the `alignas` specifier to the correct member,
`AK::Optional`'s internal buffer has been made non-zeroed by default.
GCC emitted bogus uninitialized memory access warnings, so we now use
`__builtin_launder` to tell the compiler that we know what we are doing.
This might disable some optimizations, but judging by how GCC failed to
notice that the memory's initialization is dependent on `m_has_value`,
I'm not sure that's a bad thing.

1 files changed, 4 insertions, 4 deletions

diff --git a/AK/Optional.h b/AK/Optional.h
index 6b8a987006..7348fe9a78 100644
--- a/AK/Optional.h
+++ b/AK/Optional.h
@@ -14,7 +14,7 @@
 namespace AK {
 
 template<typename T>
-class alignas(T) [[nodiscard]] Optional {
+class [[nodiscard]] Optional {
 public:
     using ValueType = T;
 
@@ -132,13 +132,13 @@ public:
     [[nodiscard]] ALWAYS_INLINE T& value()
     {
         VERIFY(m_has_value);
-        return *reinterpret_cast<T*>(&m_storage);
+        return *__builtin_launder(reinterpret_cast<T*>(&m_storage));
     }
 
     [[nodiscard]] ALWAYS_INLINE const T& value() const
     {
         VERIFY(m_has_value);
-        return *reinterpret_cast<const T*>(&m_storage);
+        return *__builtin_launder(reinterpret_cast<const T*>(&m_storage));
     }
 
     [[nodiscard]] T release_value()
@@ -164,7 +164,7 @@ public:
     ALWAYS_INLINE T* operator->() { return &value(); }
 
 private:
-    u8 m_storage[sizeof(T)] { 0 };
+    alignas(T) u8 m_storage[sizeof(T)];
     bool m_has_value { false };
 };