From 6e2745d2183fb55417b7d5c6378bac97ba73009e Mon Sep 17 00:00:00 2001
From: David Palm <dvdplm@gmail.com>
Date: Sun, 15 Dec 2019 20:59:54 +0100
Subject: [PATCH] More tests for MallocSizeOf impl for SmallVec

---
 parity-util-mem/src/impls.rs | 46 +++++++++++++++++++++++++++++-------
 1 file changed, 38 insertions(+), 8 deletions(-)

diff --git a/parity-util-mem/src/impls.rs b/parity-util-mem/src/impls.rs
index 6e9f19404..867e10cda 100644
--- a/parity-util-mem/src/impls.rs
+++ b/parity-util-mem/src/impls.rs
@@ -40,18 +40,17 @@ macro_rules! impl_smallvec {
 		where
 			T: MallocSizeOf,
 		{
-			fn size_of(&self, _: &mut MallocSizeOfOps) -> usize {
-				if self.spilled() {
-					self.capacity() * core::mem::size_of::<T>()
-				} else {
-					0
+			fn size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
+				let mut n = 0;
+				for elem in self.iter() {
+					n += elem.size_of(ops);
 				}
+				n
 			}
 		}
 	};
 }
 
-// todo[dvdplm]: check if we really need all these impls.
 impl_smallvec!(32); // kvdb uses this
 impl_smallvec!(36); // trie-db uses this
 
@@ -74,7 +73,7 @@ mod tests {
 	impl_smallvec!(3);
 
 	#[test]
-	fn test_smallvec() {
+	fn test_smallvec_stack_allocated_type() {
 		let mut v: SmallVec<[u8; 3]> = SmallVec::new();
 		let mut ops = new_malloc_size_ops();
 		assert_eq!(v.size_of(&mut ops), 0);
@@ -85,7 +84,38 @@ mod tests {
 		assert!(!v.spilled());
 		v.push(4);
 		assert!(v.spilled(), "SmallVec spills when going beyond the capacity of the inner backing array");
-		assert_eq!(v.len(), 4);
+		assert_eq!(v.size_of(&mut ops), 0); // <–– WHY NOT 4?
+	}
+
+	#[test]
+	fn test_smallvec_boxed_stack_allocated_type() {
+		let mut v: SmallVec<[Box<u8>; 3]> = SmallVec::new();
+		let mut ops = new_malloc_size_ops();
+		assert_eq!(v.size_of(&mut ops), 0);
+		v.push(Box::new(1u8));
+		v.push(Box::new(2u8));
+		v.push(Box::new(3u8));
+		assert_eq!(v.size_of(&mut ops), 3); // <– shouldn't this be 3 * pointer_size = 24?
+		assert!(!v.spilled());
+		v.push(Box::new(4u8));
+		assert!(v.spilled(), "SmallVec spills when going beyond the capacity of the inner backing array");
+		let mut ops = new_malloc_size_ops();
 		assert_eq!(v.size_of(&mut ops), 4);
 	}
+
+	#[test]
+	fn test_smallvec_heap_allocated_type() {
+		let mut v: SmallVec<[String; 3]> = SmallVec::new();
+		let mut ops = new_malloc_size_ops();
+		assert_eq!(v.size_of(&mut ops), 0);
+		v.push("COW".into());
+		v.push("PIG".into());
+		v.push("DUCK".into());
+		assert!(!v.spilled());
+		assert_eq!(v.size_of(&mut ops), 10);
+		v.push("ÖWL".into());
+		assert!(v.spilled());
+		let mut ops = new_malloc_size_ops();
+		assert_eq!(v.size_of(&mut ops), 14);
+	}
 }