qt: Fix random segfault when closing "Choose data directory" dialog

The `pickDataDirectory()` function was calling `exit(0)` to quit
the application when the user closes the dialog without choosing
a data directory.

This is a bad idea because a background thread is created (to
check free space on the drive of the currently selected datadir).
The thread is not stopped and unwound properly, resulting in a potential
race condition somewhere deep in Qt.

So replace the `exit()` by a boolean return value, and let the
stack unwind normally.

1 files changed, 4 insertions, 1 deletions

diff --git a/src/qt/intro.h b/src/qt/intro.h
index 9e2e96dc9e..ee768a7ad8 100644
--- a/src/qt/intro.h
+++ b/src/qt/intro.h
@@ -35,10 +35,13 @@ public:
     /**
      * Determine data directory. Let the user choose if the current one doesn't exist.
      *
+     * @returns true if a data directory was selected, false if the user cancelled the selection
+     * dialog.
+     *
      * @note do NOT call global GetDataDir() before calling this function, this
      * will cause the wrong path to be cached.
      */
-    static void pickDataDirectory();
+    static bool pickDataDirectory();
 
     /**
      * Determine default data directory for operating system.