Use GCC by default, fix compat w/ GCC 11 & Clang 12

SDK 21.08 only has GCC, not Clang, so we need to make sure Zypak is
compatible with it.

Makefile

@@ -6,7 +6,7 @@ LIBSYSTEMD_LDLIBS := $(shell pkg-config --libs libsystemd)
 DBUS_CFLAGS := $(shell pkg-config --cflags dbus-1)
 DBUS_LDLIBS := $(shell pkg-config --libs dbus-1)
 
-CXX := clang++
+CXX := g++
 CXXFLAGS := \
 		-fstack-protector-all -fstack-clash-protection -Wall -Werror \
 		-std=c++17 -g -pthread \

src/base/base.h

@@ -13,7 +13,6 @@ using namespace std::literals::string_literals;
 using namespace std::literals::string_view_literals;
 
 #define ATTR_NO_WARN_UNUSED __attribute__((unused))
-#define ATTR_WARN_UNUSED_RESULT __attribute__((warn_unused_result))
 
 // Inspired by the macro in base/posix/eintr_wrapper.h
 #define HANDLE_EINTR(expr)                                                                   \

src/base/socket.cc

@@ -84,7 +84,7 @@ ssize_t Socket::Read(int fd, std::byte* buffer, size_t size, ReadOptions options
           size_t nfds = GetCMsgSize(cmsg) / sizeof(int);
           options.fds->reserve(nfds);
           int* cmsg_fds = reinterpret_cast<int*>(CMSG_DATA(cmsg));
-          for (int i = 0; i < nfds; i++) {
+          for (size_t i = 0; i < nfds; i++) {
             options.fds->emplace_back(cmsg_fds[i]);
           }
         } else if (cmsg->cmsg_type == SCM_CREDENTIALS) {
@@ -149,7 +149,8 @@ bool Socket::Write(int fd, const std::byte* buffer, size_t size, WriteOptions op
     std::copy(options.fds->begin(), options.fds->end(), it);
   }
 
-  return HANDLE_EINTR(sendmsg(fd, &msg, MSG_NOSIGNAL)) == size;
+  ssize_t sent = HANDLE_EINTR(sendmsg(fd, &msg, MSG_NOSIGNAL));
+  return sent != -1 ? static_cast<size_t>(sent) == size : false;
 }
 
 // static

src/base/socket.h

@@ -6,6 +6,7 @@
 #pragma once
 
 #include <array>
+#include <optional>
 #include <vector>
 
 #include "base/base.h"

src/base/unique_fd.h

@@ -34,7 +34,7 @@ class unique_fd {
   bool invalid() const { return fd_ == kInvalidFd; }
   int get() const { return fd_; }
 
-  __attribute__((warn_unused_result)) int release() {
+  [[nodiscard]] int release() {
     int tmp = fd_;
     fd_ = kInvalidFd;
     return tmp;

src/dbus/bus_error.cc

@@ -36,8 +36,6 @@ std::string_view Error::message() const {
   return error_.message;
 }
 
-}  // namespace zypak::dbus
-
 std::ostream& operator<<(std::ostream& os, const zypak::dbus::Error& error) {
   if (error) {
     os << "[" << error.name() << "] " << error.message();
@@ -47,3 +45,5 @@ std::ostream& operator<<(std::ostream& os, const zypak::dbus::Error& error) {
 
   return os;
 }
+
+}  // namespace zypak::dbus

src/dbus/bus_error.h

@@ -32,6 +32,6 @@ class Error {
   DBusError error_;
 };
 
-}  // namespace zypak::dbus
-
 std::ostream& operator<<(std::ostream& os, const zypak::dbus::Error& error);
+
+}  // namespace zypak::dbus

src/dbus/bus_readable_message.cc

@@ -30,9 +30,9 @@ bool Signal::Test(std::string_view iface, std::string_view signal) const {
   return dbus_message_is_signal(message(), iface.data(), signal.data());
 }
 
-}  // namespace zypak::dbus
-
 std::ostream& operator<<(std::ostream& os, const zypak::dbus::InvocationError& error) {
   os << error.name().value_or("<unknown>") << ": " << error.message().value_or("<unknown>");
   return os;
 }
+
+}  // namespace zypak::dbus

src/dbus/bus_readable_message.h

@@ -4,6 +4,8 @@
 
 #pragma once
 
+#include <optional>
+
 #include "base/base.h"
 #include "base/debug.h"
 #include "dbus/bus_message.h"
@@ -113,6 +115,6 @@ class Signal : public ReadableMessage {
   bool Test(std::string_view iface, std::string_view signal) const;
 };
 
-}  // namespace zypak::dbus
-
 std::ostream& operator<<(std::ostream& os, const zypak::dbus::InvocationError& error);
+
+}  // namespace zypak::dbus

src/dbus/bus_writable_message.h

@@ -4,6 +4,8 @@
 
 #pragma once
 
+#include <optional>
+
 #include "base/base.h"
 #include "base/debug.h"
 #include "dbus/bus_message.h"

src/helper/chroot_helper.h

@@ -14,8 +14,8 @@ namespace zypak {
 
 namespace {
 
-ATTR_NO_WARN_UNUSED constexpr std::string_view kSandboxHelperFdVar = "SBX_D";
-ATTR_NO_WARN_UNUSED constexpr std::string_view kSandboxHelperPidVar = "SBX_HELPER_PID";
+ATTR_NO_WARN_UNUSED inline constexpr std::string_view kSandboxHelperFdVar = "SBX_D";
+ATTR_NO_WARN_UNUSED inline constexpr std::string_view kSandboxHelperPidVar = "SBX_HELPER_PID";
 
 }  // namespace
 

src/preload/host/spawn_strategy/supervisor.cc

@@ -71,7 +71,7 @@ Supervisor::Result Supervisor::GetExitStatus(pid_t stub_pid, int* status) {
       return Result::kNotFound;
     }
 
-    if (data->exit_status == -1) {
+    if (!data->exit_status.has_value()) {
       Debug() << "Still running, try later for " << stub_pid;
       return Result::kTryLater;
     }
@@ -90,7 +90,7 @@ Supervisor::Result Supervisor::WaitForExitStatus(pid_t stub_pid, int* status) {
     auto stub_pids_data =
         stub_pids_data_.AcquireWhen([this, stub_pid, &data](auto* stub_pids_data) {
           data = FindStubPidData(StubPid(stub_pid), *stub_pids_data);
-          return data == nullptr || data->exit_status != -1;
+          return data == nullptr || data->exit_status.has_value();
         });
 
     if (data == nullptr) {
@@ -165,7 +165,8 @@ Supervisor::FindStubPidData(StubPid stub,
 void Supervisor::ReapProcess(StubPid stub, StubPidData* data, int* status) {
   Debug() << "Reaping " << stub.pid;
 
-  *status = data->exit_status;
+  ZYPAK_ASSERT(data->exit_status.has_value());
+  *status = data->exit_status.value();
 
   if (!Socket::Write(data->notify_exit.get(), kZypakSupervisorExitReply)) {
     Errno() << "Failed to let stub process " << stub.pid << " know of exit";

src/preload/host/spawn_strategy/supervisor.h

@@ -50,7 +50,7 @@ class Supervisor {
   struct StubPidData {
     supervisor_internal::ExternalPid external = -1;
     supervisor_internal::InternalPid internal = -1;
-    std::uint32_t exit_status = -1;
+    std::optional<std::uint32_t> exit_status;
     unique_fd notify_exit;
   };
 

src/sandbox/mimic_strategy/fork.cc

@@ -123,12 +123,12 @@ std::optional<pid_t> HandleFork(nickle::Reader* reader, const unique_fd& sandbox
   if (!reader->Read<nickle::codecs::Int>(&desired_fd_count)) {
     Log() << "Failed to read fd count";
     return {};
-  } else if (desired_fd_count != fds.size()) {
-    Log() << "Given " << fds.size() << " fds, but pickle wants " << desired_fd_count;
-    return {};
   } else if (desired_fd_count < 1) {
     Log() << "Too few FDs " << fds.size();
     return {};
+  } else if (static_cast<size_t>(desired_fd_count) != fds.size()) {
+    Log() << "Given " << fds.size() << " fds, but pickle wants " << desired_fd_count;
+    return {};
   }
 
   unique_fd pid_oracle(std::move(fds[0]));