From edda77cf7f4e9803a8f5bd7a9de50f08959d4133 Mon Sep 17 00:00:00 2001
From: trivernis <trivernis@protonmail.com>
Date: Sun, 13 Mar 2022 21:28:04 +0100
Subject: [PATCH] Reduced amount of null pointers in create_object

Signed-off-by: trivernis <trivernis@protonmail.com>
---
 src/lib.rs    | 12 +++++++-----
 src/macros.rs | 16 ++++++++++------
 2 files changed, 17 insertions(+), 11 deletions(-)

diff --git a/src/lib.rs b/src/lib.rs
index 9d55232..d180548 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -63,7 +63,9 @@ impl MultitraitObject {
             original_typeid: TypeId::of::<T>(),
             traits: Default::default(),
         };
-        this._register::<dyn Any>(any_vtable);
+        unsafe {
+            this._register::<dyn Any>(any_vtable);
+        }
 
         this
     }
@@ -85,6 +87,7 @@ impl MultitraitObject {
             None
         } else {
             unsafe {
+                // SAFETY: We've checked the size of the pointer
                 self._downcast_trait_mut::<T1>()
             }
         }
@@ -96,6 +99,7 @@ impl MultitraitObject {
             None
         } else {
             unsafe {
+                // SAFETY: We've checked the size of the pointer
                 self._downcast_boxed_trait::<T1>()
             }
         }
@@ -146,14 +150,14 @@ impl MultitraitObject {
 
     #[doc(hidden)]
     #[inline]
-    pub fn _register<T2: 'static + ?Sized>(&mut self, vtable_ptr: *const ()) {
+    pub unsafe fn _register<T2: 'static + ?Sized>(&mut self, vtable_ptr: *const ()) {
+        // this function is considers unsafe as there is no validation of the given raw pointer
         self.traits.insert(TypeId::of::<T2>(), vtable_ptr);
     }
 
     #[doc(hidden)]
     #[inline]
     unsafe fn _downcast_trait<T1: 'static + ?Sized>(&self) -> Option<&T1> {
-        // SAFETY: Creating a fat pointer from the given v-table and data has no side effects
         let vptr = *self.traits.get(&TypeId::of::<T1>())?;
         let fat_pointer = FatPointer { data: self.data, vptr };
         let value = std::mem::transmute::<_, &&T1>(&fat_pointer);
@@ -164,7 +168,6 @@ impl MultitraitObject {
     #[doc(hidden)]
     #[inline]
     unsafe fn _downcast_trait_mut<T1: 'static + ?Sized>(&mut self) -> Option<&mut T1> {
-        // SAFETY: Creating a fat pointer from the given v-table and data has no side effects
         let vptr = *self.traits.get(&TypeId::of::<T1>())?;
         let mut fat_pointer = FatPointer { data: self.data, vptr };
         let value = std::mem::transmute::<_, &mut &mut T1>(&mut fat_pointer);
@@ -175,7 +178,6 @@ impl MultitraitObject {
     #[doc(hidden)]
     #[inline]
     unsafe fn _downcast_boxed_trait<T1: 'static + ?Sized>(&mut self) -> Option<Box<T1>> {
-        // SAFETY: Creating a fat pointer from the given v-table and data has no side effects
         let vptr = *self.traits.get(&TypeId::of::<T1>())?;
         let fat_pointer = FatPointer { data: self.data, vptr };
         let value = std::mem::transmute::<_, *const *mut T1>(&fat_pointer);
diff --git a/src/macros.rs b/src/macros.rs
index 854e07b..d0f78de 100644
--- a/src/macros.rs
+++ b/src/macros.rs
@@ -20,7 +20,10 @@ macro_rules! impl_trait_object {
             fn into_multitrait(self) -> $crate::MultitraitObject {
                 let mut mto = $crate::MultitraitObject::new(self);
                 $(
-                    mto._register::<$trt>($crate::__fat_pointer!($obj as $trt).vptr);
+                    unsafe {
+                        // SAFETY: We're only passing v-tables associated with the given type
+                        mto._register::<$trt>($crate::__fat_pointer!($obj as $trt).vptr);
+                    }
                 )*
 
                 mto
@@ -58,12 +61,13 @@ macro_rules! create_object {
             };
             let mut mto = $crate::MultitraitObject::new($v);
             $(
-                let vptr = unsafe {
+                unsafe {
                     // SAFETY: We're never accessing the null value
-                    let ptr = $crate::null_ptr(&*null_ptr) as *const $t;
-                    std::mem::transmute::<_, $crate::FatPointer>(ptr).vptr
-                };
-                mto._register::<$t>(vptr);
+                    let ptr = null_ptr as *const $t;
+                    let vptr = std::mem::transmute::<_, $crate::FatPointer>(ptr).vptr;
+                    // SAFETY: We're only passing v-tables associated with the given type
+                    mto._register::<$t>(vptr);
+                }
             )+
             mto
         }