sniffer: fix mangled lines on stdout output

apps/caracal.cpp

@@ -131,7 +131,6 @@ int main(int argc, char** argv) {
     spdlog::set_default_logger(spdlog::stderr_color_st(""));
 
     spdlog::info("Reading from stdin, press CTRL+D to stop...");
-    std::ios::sync_with_stdio(false);
     caracal::Prober::probe(config, std::cin);
   } catch (const std::exception& e) {
     auto type = caracal::Utilities::demangle(typeid(e).name());

src/sniffer.cpp

@@ -11,6 +11,10 @@
 #include <filesystem>
 #include <iostream>
 #include <optional>
+#ifndef __APPLE__
+// Currently not available on macOS
+#include <syncstream>
+#endif
 #include <thread>
 
 namespace fs = std::filesystem;
@@ -70,14 +74,19 @@ void Sniffer::start() noexcept {
   std::cout << (Reply::csv_header() + "\n");
   auto handler = [this](Tins::Packet &packet) {
     auto reply = Parser::parse(packet);
+#ifdef __APPLE__
+    auto stdout = std::cout;
+#else
+    auto stdout = std::osyncstream(std::cout);
+#endif
 
     if (reply && (!integrity_check_ || reply->is_valid(caracal_id_))) {
       spdlog::trace(reply.value());
       statistics_.icmp_messages_all.insert(reply->reply_src_addr);
       if (reply->is_time_exceeded()) {
         statistics_.icmp_messages_path.insert(reply->reply_src_addr);
       }
-      std::cout << (reply->to_csv(meta_round_.value_or("1")) + "\n");
+      stdout << (reply->to_csv(meta_round_.value_or("1")) + "\n");
     } else {
       auto data = packet.pdu()->serialize();
       spdlog::trace("invalid_packet_hex={:02x}", fmt::join(data, ""));