Use read_unaligned instead of read in transmute_copy

newpavlov · web-flow · commit 4210ccad1407 · 2018-10-13T22:01:59.000Z
Closes: #55044 This change could result in performance regression on non-x86 platforms. Alternative would be to update `transmute_copy` with alignment requirements.
diff --git a/src/libcore/mem.rs b/src/libcore/mem.rs
@@ -818,7 +818,7 @@ pub fn drop<T>(_x: T) { }
 #[inline]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub unsafe fn transmute_copy<T, U>(src: &T) -> U {
-    ptr::read(src as *const T as *const U)
+    ptr::read_unaligned(src as *const T as *const U)
 }
 
 /// Opaque type representing the discriminant of an enum.

Original file line number	Diff line number	Diff line change
`@@ -818,7 +818,7 @@ pub fn drop<T>(_x: T) { }`
`818`	`818`	`#[inline]`
`819`	`819`	`#[stable(feature = "rust1", since = "1.0.0")]`
`820`	`820`	`pub unsafe fn transmute_copy<T, U>(src: &T) -> U {`
`821`		`- ptr::read(src as const T as const U)`
	`821`	`+ ptr::read_unaligned(src as const T as const U)`
`822`	`822`	`}`
`823`	`823`
`824`	`824`	`/// Opaque type representing the discriminant of an enum.`