From 3099a6bf2add35ac6a0c7ce4cbb6c794d6269d19 Mon Sep 17 00:00:00 2001
From: Daniel Bertalan <dani@danielbertalan.dev>
Date: Thu, 15 Jul 2021 13:50:55 +0200
Subject: [PATCH] Kernel+AK: Generate compile-time error for non-sized `delete`

This is a much more ergonomic option than getting a
`VERIFY_NOT_REACHED()` failure at run-time. I encountered this issue
with Clang, where sized deallocation is not the default due to ABI
breakage concerns.

Note that we can't simply just not declare these functions, because the
C++ standard states:
> If this function with size parameter is defined, the program shall
> also define the version without the size parameter.
---
 AK/Platform.h         | 9 +++++++++
 Kernel/Heap/kmalloc.h | 5 +++--
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/AK/Platform.h b/AK/Platform.h
index 2924f53cc30..8f9243f25f9 100644
--- a/AK/Platform.h
+++ b/AK/Platform.h
@@ -59,6 +59,15 @@
 #endif
 #define NAKED __attribute__((naked))
 
+#ifdef DISALLOW
+#    undef DISALLOW
+#endif
+#ifdef __clang__
+#    define DISALLOW(message) __attribute__((diagnose_if(1, message, "error")))
+#else
+#    define DISALLOW(message) __attribute__((error(message)))
+#endif
+
 // GCC doesn't have __has_feature but clang does
 #ifndef __has_feature
 #    define __has_feature(...) 0
diff --git a/Kernel/Heap/kmalloc.h b/Kernel/Heap/kmalloc.h
index 2c005d2a80f..f05766ff21b 100644
--- a/Kernel/Heap/kmalloc.h
+++ b/Kernel/Heap/kmalloc.h
@@ -64,14 +64,15 @@ inline void* operator new[](size_t, void* p) { return p; }
 [[nodiscard]] void* operator new(size_t size, std::align_val_t);
 [[nodiscard]] void* operator new(size_t size, std::align_val_t, const std::nothrow_t&) noexcept;
 
-void operator delete(void* ptr) noexcept;
+void operator delete(void* ptr) noexcept DISALLOW("All deletes in the kernel should have a known size.");
 void operator delete(void* ptr, size_t) noexcept;
+void operator delete(void* ptr, std::align_val_t) noexcept DISALLOW("All deletes in the kernel should have a known size.");
 void operator delete(void* ptr, size_t, std::align_val_t) noexcept;
 
 [[nodiscard]] void* operator new[](size_t size);
 [[nodiscard]] void* operator new[](size_t size, const std::nothrow_t&) noexcept;
 
-void operator delete[](void* ptrs) noexcept;
+void operator delete[](void* ptrs) noexcept DISALLOW("All deletes in the kernel should have a known size.");
 void operator delete[](void* ptr, size_t) noexcept;
 
 [[gnu::malloc, gnu::returns_nonnull, gnu::alloc_size(1)]] void* kmalloc(size_t);