Release 1.7.1

CHANGELOG.md

@@ -1,3 +1,7 @@
+## [1.7.1] - 2026-10-11
+
+- Fix RLC and RRC on memory writing values over a byte, which could stop the Spinel browser build
+
 ## [1.7.0] - 2026-10-10
 
 - Require Ruby 4.0 or higher

Gemfile.lock

@@ -1,7 +1,7 @@
 PATH
   remote: .
   specs:
-    rubyboy (1.7.0)
+    rubyboy (1.7.1)
       ffi (~> 1.16, >= 1.16.3)
 
 GEM

lib/rubyboy/cpu.rb

@@ -1071,7 +1071,7 @@ def reti(cycles:)
 
     def rlc8(x, cycles:)
       value = get_value(x)
-      value = (value << 1) | (value >> 7)
+      value = ((value << 1) | (value >> 7)) & 0xff
       set_value(x, value)
       update_flags(
         z: value == 0,
@@ -1085,7 +1085,7 @@ def rlc8(x, cycles:)
 
     def rrc8(x, cycles:)
       value = get_value(x)
-      value = (value >> 1) | (value << 7)
+      value = ((value >> 1) | (value << 7)) & 0xff
       set_value(x, value)
       update_flags(
         z: value == 0,

lib/rubyboy/version.rb

@@ -1,5 +1,5 @@
 # frozen_string_literal: true
 
 module Rubyboy
-  VERSION = '1.7.0'
+  VERSION = '1.7.1'
 end

spec/rubyboy/cpu_spec.rb

@@ -0,0 +1,29 @@
+# frozen_string_literal: true
+
+RSpec.describe Rubyboy::Cpu do
+  let(:memory) { Array.new(0x10000, 0) }
+  let(:cpu) do
+    bus = instance_double(Rubyboy::Bus)
+    allow(bus).to receive(:read_byte) { |addr| memory[addr] }
+    allow(bus).to receive(:read_word) { |addr| memory[addr] | (memory[addr + 1] << 8) }
+    allow(bus).to receive(:write_byte) { |addr, value| memory[addr] = value }
+    described_class.new(bus, Rubyboy::Interrupt.new)
+  end
+
+  # LD HL, 0xc000, then the CB-prefixed rotate eight times: the byte comes back.
+  def rotate_hl_eight_times(cb_opcode, value)
+    program = [0x21, 0x00, 0xc0] + ([0xcb, cb_opcode] * 8)
+    memory[0x0100, program.size] = program
+    memory[0xc000] = value
+    9.times { cpu.exec }
+    memory[0xc000]
+  end
+
+  it 'keeps RLC (HL) within a byte' do
+    expect(rotate_hl_eight_times(0x06, 0x81)).to eq(0x81)
+  end
+
+  it 'keeps RRC (HL) within a byte' do
+    expect(rotate_hl_eight_times(0x0e, 0x81)).to eq(0x81)
+  end
+end