Fix bug 1784

http://bugzilla.lyx.org/show_bug.cgi?id=1784

git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@26737 a592a061-630c-0410-9148-cb99ea01b6c8

diff --git a/src/Server.cpp b/src/Server.cpp
index 99be0afa5a4f1dda97e35906e0a99fe2af299293..7d4b0c3b001af3dc26c0183bdf779cbb80018d50 100644 (file)
--- a/src/Server.cpp
+++ b/src/Server.cpp
@@ -252,6 +252,12 @@ void LyXComm::read_ready()
        int const charbuf_size = 100;
        char charbuf[charbuf_size];
 
+       // As O_NONBLOCK is set, until no data is available for reading,
+       // read() doesn't block but returns -1 and set errno to EAGAIN.
+       // After a client that opened the pipe for writing, closes it
+       // (and no other client is using the pipe), read() would always
+       // return 0 and thus the connection has to be reset.
+
        errno = 0;
        int status;
        // the single = is intended here.
@@ -273,12 +279,13 @@ void LyXComm::read_ready()
                                        clientcb_(client_, cmd);
                                        //\n or not \n?
                        }
-               }
-               if (errno == EAGAIN) {
-                       errno = 0;
-                       return;
-               }
-               if (errno != 0) {
+               } else {
+                       if (errno == EAGAIN) {
+                               // Nothing to read, continue
+                               errno = 0;
+                               return;
+                       }
+                       // An error occurred, better bailing out
                        LYXERR0("LyXComm: " << strerror(errno));
                        if (!read_buffer_.empty()) {
                                LYXERR0("LyXComm: truncated command: " << read_buffer_);
@@ -288,8 +295,9 @@ void LyXComm::read_ready()
                }
        }
 
-       // The connection gets reset in errno != EAGAIN
-       // Why does it need to be reset if errno == 0?
+       // The connection gets reset when read() returns 0 (meaning that the
+       // last client closed the pipe) or an error occurred, in which case
+       // read() returns -1 and errno != EAGAIN.
        closeConnection();
        openConnection();
        errno = 0;