[stdlib] correct MutableRawSpan sizing

glessard · glessard · commit cb390140d686 · 2025-04-10T10:31:18.000-07:00
diff --git a/stdlib/public/core/Span/MutableRawSpan.swift b/stdlib/public/core/Span/MutableRawSpan.swift
@@ -109,7 +109,8 @@ extension MutableRawSpan {
     let (start, count) = unsafe (elements._pointer, elements._count)
     let span = unsafe MutableRawSpan(
       _unchecked: start,
-      byteCount: count &* MemoryLayout<Element>.stride
+      byteCount: count == 1 ? MemoryLayout<Element>.size
+                 : count &* MemoryLayout<Element>.stride
     )
     self = unsafe _overrideLifetime(span, mutating: &elements)
   }

Original file line number	Diff line number	Diff line change
`@@ -109,7 +109,8 @@ extension MutableRawSpan {`
`109`	`109`	`let (start, count) = unsafe (elements._pointer, elements._count)`
`110`	`110`	`let span = unsafe MutableRawSpan(`
`111`	`111`	`_unchecked: start,`
`112`		`- byteCount: count &* MemoryLayout<Element>.stride`
	`112`	`+ byteCount: count == 1 ? MemoryLayout<Element>.size`
	`113`	`+ : count &* MemoryLayout<Element>.stride`
`113`	`114`	`)`
`114`	`115`	`self = unsafe _overrideLifetime(span, mutating: &elements)`
`115`	`116`	`}`