From 2b73c28cec9a5c75ab064f1ebd88b12aa64d22dd Mon Sep 17 00:00:00 2001
From: Ryan Liptak <squeek502@hotmail.com>
Date: Thu, 28 Aug 2025 00:26:57 -0700
Subject: [PATCH] Reader.appendRemaining: Take ownership of the full allocated
 slice

Before this commit, calling appendRemaining with an ArrayList where list.items.len != list.capacity could result in illegal behavior if the Writer.Allocating resized the list during the appendRemaining call.

Fixes #25057
---
 lib/std/Io/Reader.zig | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/std/Io/Reader.zig b/lib/std/Io/Reader.zig
index 5e08ad6d0c..f6cb22cb4b 100644
--- a/lib/std/Io/Reader.zig
+++ b/lib/std/Io/Reader.zig
@@ -308,7 +308,7 @@ pub fn appendRemaining(
     list: *ArrayList(u8),
     limit: Limit,
 ) LimitedAllocError!void {
-    var a: std.Io.Writer.Allocating = .initOwnedSlice(gpa, list.items);
+    var a: std.Io.Writer.Allocating = .initOwnedSlice(gpa, list.allocatedSlice());
     a.writer.end = list.items.len;
     list.* = .empty;
     defer {
@@ -332,7 +332,7 @@ pub fn appendRemaining(
 pub const UnlimitedAllocError = Allocator.Error || ShortError;
 
 pub fn appendRemainingUnlimited(r: *Reader, gpa: Allocator, list: *ArrayList(u8)) UnlimitedAllocError!void {
-    var a: std.Io.Writer.Allocating = .initOwnedSlice(gpa, list.items);
+    var a: std.Io.Writer.Allocating = .initOwnedSlice(gpa, list.allocatedSlice());
     a.writer.end = list.items.len;
     list.* = .empty;
     defer {