Userland: Resolve unused-but-set-varaible warnings

These are almost always bugs, so enable globally.

Remove unused counter variables in SystemMonitor and disk_benchmark.

CMakeLists.txt

@@ -200,7 +200,6 @@ elseif (CMAKE_CXX_COMPILER_ID MATCHES "Clang$")
  add_compile_options(-Wno-implicit-const-int-float-conversion)
  add_compile_options(-Wno-null-pointer-subtraction)
  add_compile_options(-Wno-unneeded-internal-declaration)
- add_compile_options(-Wno-unused-but-set-variable)
  add_compile_options(-Wno-unused-const-variable)
  add_compile_options(-Wno-unused-function)
  add_compile_options(-Wno-unused-private-field)

Userland/Applications/SystemMonitor/ProcessModel.cpp

@@ -334,7 +334,6 @@ void ProcessModel::update()
  auto all_processes = Core::ProcessStatisticsReader::get_all(m_proc_all);
 
  HashTable<int> live_tids;
- u64 sum_time_scheduled = 0, sum_time_scheduled_kernel = 0;
  u64 total_time_scheduled_diff = 0;
  if (all_processes.has_value()) {
  if (m_has_total_scheduled_time)
@@ -382,8 +381,6 @@ void ProcessModel::update()
  state.cpu_percent = 0;
  state.priority = thread.priority;
  state.state = thread.state;
- sum_time_scheduled += thread.time_user + thread.time_kernel;
- sum_time_scheduled_kernel += thread.time_kernel;
  auto& thread_data = *m_threads.ensure(thread.tid, [] { return make<Thread>(); });
  thread_data.previous_state = move(thread_data.current_state);
  thread_data.current_state = move(state);

Userland/Utilities/disk_benchmark.cpp

@@ -147,7 +147,7 @@ Optional<Result> benchmark(const String& filename, int file_size, int block_size
  auto timer = Core::ElapsedTimer::start_new();
 
  ssize_t total_written = 0;
- for (ssize_t j = 0; j < file_size; j += block_size) {
+ while (total_written < file_size) {
  auto nwritten = write(fd, buffer.data(), block_size);
  if (nwritten < 0) {
  perror("write");