linux: terminate on SIGTERM/SIGINT in the host scaffold and example

CHANGELOG.md

@@ -2,6 +2,13 @@
 
 ## Unreleased
 
+- Linux hosts now terminate on SIGTERM/SIGINT. The host scaffold and the
+  Taskboard example install Rivet's shutdown hook so a termination signal
+  runs the same orderly backend shutdown as the GTK shutdown signal and
+  then exits; previously the embedded backend died on the signal while the
+  GTK process stayed up, leaving a window that could not search or run
+  anything (observed on Fulcrum 0.4.1: `kill` left a half-dead app that
+  only SIGKILL would remove).
 - Honor `linux-binary-name` in `rivet.rktd`: the Linux build stage, package
   staging, verification, and launch smoke now use the configured executable
   name instead of the hardcoded scaffold name `RivetHost` (default

examples/taskboard/linux/src/main.cpp

@@ -6,6 +6,7 @@
 #include <algorithm>
 #include <atomic>
 #include <cstdint>
+#include <cstdio>
 #include <filesystem>
 #include <memory>
 #include <mutex>
@@ -527,12 +528,22 @@ void on_shutdown(GApplication*, gpointer) {
   if (g_state.backend) g_state.backend->stop();
 }
 
+// SIGTERM/SIGINT bypass the GTK main loop; run the same orderly shutdown
+// the GTK shutdown signal would have run, then the hook hard-exits.
+void perform_orderly_shutdown() { on_shutdown(nullptr, nullptr); }
+
 }  // namespace
 
 int main(int argc, char** argv) {
   auto* app = gtk_application_new("dev.rivet.taskboard", G_APPLICATION_DEFAULT_FLAGS);
   g_signal_connect(app, "activate", G_CALLBACK(on_activate), nullptr);
   g_signal_connect(app, "shutdown", G_CALLBACK(on_shutdown), nullptr);
+  try {
+    rivet::system::InstallShutdownHook(perform_orderly_shutdown);
+  } catch (std::exception const& error) {
+    std::fputs((std::string{"shutdown hook unavailable: "} + error.what() + "\n").c_str(),
+               stderr);
+  }
   int const status = g_application_run(G_APPLICATION(app), argc, argv);
   g_object_unref(app);
   return status;

platform/linux/host/src/main.cpp

@@ -6,14 +6,17 @@
 
 #include <atomic>
 #include <cstdint>
+#include <cstdio>
 #include <filesystem>
+#include <functional>
 #include <memory>
 #include <mutex>
 #include <optional>
 #include <string>
 #include <thread>
 
 #include "GeneratedBackend.hpp"
+#include "system_services.hpp"
 #include "theme.hpp"
 
 namespace {
@@ -264,13 +267,26 @@ void on_shutdown(GApplication*, gpointer) {
   }
 }
 
+// SIGTERM/SIGINT bypass the GTK main loop, so the shutdown signal handler
+// alone would leave the window alive over a dead backend. The watcher
+// thread runs this same cleanup and then hard-exits; keep it synchronous
+// and allocation-light.
+void perform_orderly_shutdown() { on_shutdown(nullptr, nullptr); }
+
 }  // namespace
 
 int main(int argc, char** argv) {
   auto* app = gtk_application_new("dev.rivet.host",
                                   G_APPLICATION_DEFAULT_FLAGS);
   g_signal_connect(app, "activate", G_CALLBACK(on_activate), nullptr);
   g_signal_connect(app, "shutdown", G_CALLBACK(on_shutdown), nullptr);
+  try {
+    rivet::system::InstallShutdownHook(perform_orderly_shutdown);
+  } catch (std::exception const& error) {
+    std::fputs((std::string{"shutdown hook unavailable: "} + error.what() +
+                "\n").c_str(),
+               stderr);
+  }
   int const status = g_application_run(G_APPLICATION(app), argc, argv);
   g_object_unref(app);
   return status;