lspserver: stop connection while the client process died. (#437)

lspserver/src/Connection.cpp

@@ -3,17 +3,29 @@
 #include "lspserver/Protocol.h"
 
 #include <llvm/ADT/SmallString.h>
+#include <llvm/Support/CommandLine.h>
 
 #include <poll.h>
 #include <sys/poll.h>
 #include <sys/stat.h>
 
+#include <csignal>
 #include <cstdint>
 #include <cstdio>
 #include <memory>
 #include <optional>
 #include <system_error>
 
+namespace {
+
+llvm::cl::opt<int> ClientProcessID{
+    "clientProcessId",
+    llvm::cl::desc(
+        "Client process ID, if this PID died, the server should exit."),
+    llvm::cl::init(getppid())};
+
+} // namespace
+
 namespace lspserver {
 
 static llvm::json::Object encodeError(llvm::Error Error) {
@@ -158,6 +170,11 @@ bool readLine(int fd, const std::atomic<bool> &Close,
         Line += Ch;
       }
     }
+
+    if (kill(ClientProcessID, 0) < 0) {
+      // Parent died.
+      return false;
+    }
   }
 }