[stdlib] guard against underflow

glessard · glessard · commit 5e9c3f4a1d8b · 2025-08-16T04:13:15.000-07:00
diff --git a/stdlib/public/core/Span/OutputSpan.swift b/stdlib/public/core/Span/OutputSpan.swift
@@ -315,6 +315,7 @@ extension OutputSpan where Element: ~Copyable {
   @_alwaysEmitIntoClient
   @lifetime(self: copy self)
   public mutating func removeAll() {
+    guard count > 0 else { return }
     _ = unsafe _start().withMemoryRebound(to: Element.self, capacity: _count) {
       unsafe $0.deinitialize(count: _count)
     }

Original file line number	Diff line number	Diff line change
`@@ -315,6 +315,7 @@ extension OutputSpan where Element: ~Copyable {`
`315`	`315`	`@_alwaysEmitIntoClient`
`316`	`316`	`@lifetime(self: copy self)`
`317`	`317`	`public mutating func removeAll() {`
	`318`	`+ guard count > 0 else { return }`
`318`	`319`	`_ = unsafe _start().withMemoryRebound(to: Element.self, capacity: _count) {`
`319`	`320`	`unsafe $0.deinitialize(count: _count)`
`320`	`321`	`}`