fix: some crashes

src/modules/wayfire/backend.cpp

@@ -9,6 +9,7 @@
 #include <bit>
 #include <cstdint>
 #include <cstdlib>
+#include <cstring>
 #include <exception>
 #include <ranges>
 #include <thread>
@@ -32,7 +33,13 @@ auto pack_and_write(Sock& sock, std::string&& buf) -> void {
 
 auto read_exact(Sock& sock, size_t n) -> std::string {
   auto buf = std::string(n, 0);
-  for (size_t i = 0; i < n;) i += read(sock.fd, &buf[i], n - i);
+  for (size_t i = 0; i < n;) {
+    auto r = read(sock.fd, &buf[i], n - i);
+    if (r <= 0) {
+      throw std::runtime_error("Wayfire IPC: read failed");
+    }
+    i += static_cast<size_t>(r);
+  }
   return buf;
 }
 
@@ -53,6 +60,9 @@ auto State::Wset::locate_ws(const Json::Value& geo) -> Workspace& {
 }
 
 auto State::Wset::locate_ws(const Json::Value& geo) const -> const Workspace& {
+  if (!output.has_value()) {
+    throw std::runtime_error("Wayfire IPC: wset has no output assigned");
+  }
   const auto& out = output.value().get();
   auto [qx, rx] = std::div(geo["x"].asInt(), out.w);
   auto [qy, ry] = std::div(geo["y"].asInt(), out.h);
@@ -88,7 +98,10 @@ auto State::update_view(const Json::Value& view) -> void {
 
 auto IPC::get_instance() -> std::shared_ptr<IPC> {
   auto p = instance.lock();
-  if (!p) instance = p = std::shared_ptr<IPC>(new IPC);
+  if (!p) {
+    instance = p = std::shared_ptr<IPC>(new IPC);
+    p->start();
+  }
   return p;
 }
 
@@ -116,7 +129,9 @@ auto IPC::connect() -> Sock {
 }
 
 auto IPC::receive(Sock& sock) -> Json::Value {
-  auto len = *reinterpret_cast<uint32_t*>(read_exact(sock, 4).data());
+  auto len_buf = read_exact(sock, 4);
+  uint32_t len;
+  std::memcpy(&len, len_buf.data(), sizeof(len));
   if constexpr (std::endian::native != std::endian::little) len = byteswap(len);
   auto buf = read_exact(sock, len);
 
@@ -153,15 +168,15 @@ auto IPC::start() -> void {
   send("window-rules/get-focused-view", {});
   send("window-rules/get-focused-output", {});
 
-  std::thread([&] {
+  std::thread([self = shared_from_this()] {
     auto sock = connect();
 
     {
       Json::Value json;
       json["method"] = "window-rules/events/watch";
 
-      pack_and_write(sock, Json::writeString(writer_builder, json));
-      if (receive(sock)["result"] != "ok") {
+      pack_and_write(sock, Json::writeString(self->writer_builder, json));
+      if (self->receive(sock)["result"] != "ok") {
         spdlog::error(
             "Wayfire IPC: method \"window-rules/events/watch\""
             " have failed");
@@ -169,10 +184,10 @@ auto IPC::start() -> void {
       }
     }
 
-    while (auto json = receive(sock)) {
+    while (auto json = self->receive(sock)) {
       auto ev = json["event"].asString();
       spdlog::debug("Wayfire IPC: received event \"{}\"", ev);
-      root_event_handler(ev, json);
+      self->root_event_handler(ev, json);
     }
   }).detach();
 }