Dialog.c: fix format-truncation warning

Dialog.c: In function ‘nxagentLaunchDialog’:
Dialog.c:320:53: warning: ‘%s’ directive output may be truncated writing up to 1023 bytes into a region of size 256 [-Wformat-truncation=]
     snprintf(dialogDisplay, sizeof(dialogDisplay), "%s", nxagentDisplayName);
                                                     ^~   ~~~~~~~~~~~~~~~~~~
Dialog.c:320:5: note: ‘snprintf’ output between 1 and 1024 bytes into a destination of size 256
     snprintf(dialogDisplay, sizeof(dialogDisplay), "%s", nxagentDisplayName);
     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

1 files changed, 14 insertions, 4 deletions

diff --git a/nx-X11/programs/Xserver/hw/nxagent/Dialog.c b/nx-X11/programs/Xserver/hw/nxagent/Dialog.c
index c20a6a475..2d4eb6229 100644
--- a/nx-X11/programs/Xserver/hw/nxagent/Dialog.c
+++ b/nx-X11/programs/Xserver/hw/nxagent/Dialog.c
@@ -40,6 +40,7 @@
 #include "Args.h"
 #include "Display.h"
 #include "Dialog.h"
+#include "Utils.h"
 
 #include <nx/NX.h>
 #include "compext/Compext.h"
@@ -182,7 +183,6 @@ void nxagentResetDialog(int pid)
 
 void nxagentLaunchDialog(DialogType dialogType)
 {
-  char dialogDisplay[256];
   sigset_t set, oldSet;
   int *pid;
   char *type;
@@ -302,13 +302,23 @@ void nxagentLaunchDialog(DialogType dialogType)
   fprintf(stderr, "nxagentLaunchDialog: Launching dialog type [%d] message [%s].\n", type, message);
   #endif
 
+  char *dialogDisplay = NULL;
+  int len = 0;
   if (dialogType == DIALOG_FAILED_RECONNECTION)
   {
-    snprintf(dialogDisplay, sizeof(dialogDisplay), "%s", nxagentDisplayName);
+    len = asprintf(&dialogDisplay, "%s", nxagentDisplayName);
   }
   else
   {
-    snprintf(dialogDisplay, sizeof(dialogDisplay), ":%s", display);
+    len = asprintf(&dialogDisplay, ":%s", display);
+  }
+
+  if (len == -1)
+  {
+    #ifdef DEBUG
+    fprintf(stderr, "%s: could not allocate display string.\n", __func__);
+    #endif
+    return;
   }
 
   /*
@@ -329,7 +339,7 @@ void nxagentLaunchDialog(DialogType dialogType)
               DECODE_DIALOG_TYPE(dialogType), *pid, dialogDisplay);
   #endif
 
-  dialogDisplay[0] = '\0';
+  SAFE_free(dialogDisplay);
 
   /*
    * Restore the previous set of blocked signal.