qt follow stream: don't crash when saving to an non-writable file

When the user clicks Save As in the Follow Stream window, check that the
selected target file can be opened for writing. Bring up a warning box
if the file is not writable.

Change-Id: I76e67b064377dd432d3b14592f5096b99d9968c0
Reviewed-on: https://code.wireshark.org/review/15536
Reviewed-by: Michael Mann <mmann78@netscape.net>

1 files changed, 6 insertions, 2 deletions

diff --git a/ui/qt/follow_stream_dialog.cpp b/ui/qt/follow_stream_dialog.cpp
index 443d10b0e9..29ec2b83fb 100644
--- a/ui/qt/follow_stream_dialog.cpp
+++ b/ui/qt/follow_stream_dialog.cpp
@@ -266,10 +266,14 @@ void FollowStreamDialog::saveAs()
 {
     QString file_name = QFileDialog::getSaveFileName(this, wsApp->windowTitleString(tr("Save Stream Content As" UTF8_HORIZONTAL_ELLIPSIS)));
     if (!file_name.isEmpty()) {
-        file_.setFileName(file_name);
-        file_.open(QIODevice::WriteOnly);
         QTextStream out(&file_);
 
+        if (!file_.open(QIODevice::WriteOnly)) {
+            open_failure_alert_box(file_name.toUtf8().constData(), errno, TRUE);
+            return;
+        }
+        file_.setFileName(file_name);
+
         save_as_ = true;
 
         readStream();