From ae516276684aeb3b7886013ff8a00a5367e530fb Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=B6nke=20Holz?= <soenke.holz@serenityos.org>
Date: Thu, 19 Mar 2026 11:14:13 +0100
Subject: [PATCH] AK: Format `char` as `unsigned char` on non-x86

`char` isn't signed in the AArch64 and RISC-V ABIs.
---
 AK/Format.cpp           |  9 +++++++--
 Tests/AK/TestFormat.cpp | 11 +++++++++++
 2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/AK/Format.cpp b/AK/Format.cpp
index 8fc79b3cd9c..bd70ac76ded 100644
--- a/AK/Format.cpp
+++ b/AK/Format.cpp
@@ -949,8 +949,13 @@ ErrorOr<void> Formatter<char>::format(FormatBuilder& builder, char value)
 {
     if (m_mode == Mode::Binary || m_mode == Mode::BinaryUppercase || m_mode == Mode::Decimal || m_mode == Mode::Octal || m_mode == Mode::Hexadecimal || m_mode == Mode::HexadecimalUppercase) {
         // Trick: signed char != char. (Sometimes weird features are actually helpful.)
-        Formatter<signed char> formatter { *this };
-        return formatter.format(builder, static_cast<signed char>(value));
+        if constexpr (IsSigned<char>) {
+            Formatter<signed char> formatter { *this };
+            return formatter.format(builder, static_cast<signed char>(value));
+        } else {
+            Formatter<unsigned char> formatter { *this };
+            return formatter.format(builder, static_cast<unsigned char>(value));
+        }
     } else {
         Formatter<StringView> formatter { *this };
         return formatter.format(builder, { &value, 1 });
diff --git a/Tests/AK/TestFormat.cpp b/Tests/AK/TestFormat.cpp
index f96de7c2078..0797893b2c8 100644
--- a/Tests/AK/TestFormat.cpp
+++ b/Tests/AK/TestFormat.cpp
@@ -223,6 +223,17 @@ struct AK::Formatter<B> : Formatter<StringView> {
     }
 };
 
+TEST_CASE(format_character_as_integer)
+{
+    EXPECT_EQ(ByteString::formatted("{:x}", 'A'), "41");
+
+    if constexpr (IsSigned<char>) {
+        EXPECT_EQ(ByteString::formatted("{:x}", '\x86'), "-7a");
+    } else {
+        EXPECT_EQ(ByteString::formatted("{:x}", '\x86'), "86");
+    }
+}
+
 TEST_CASE(format_if_supported)
 {
     EXPECT_EQ(ByteString::formatted("{}", FormatIfSupported { A {} }), "?");