[gnome-sudoku] qqwing-wrapper: seed RNG

[Michael Catanzaro <mcatanzaro src gnome org>]

commit 7d404bebb77ae63eb901cc6f2c0131eec84570d0
Author: Michael Catanzaro <mcatanzaro gnome org>
Date:   Mon Jul 11 22:55:42 2016 -0500

    qqwing-wrapper: seed RNG
    
    So we don't repeat same puzzles each time Sudoku is started.
    
    Credit to Yuri Khan for discovering and debugging this issue (and for
    submitting a different fix).
    
    https://bugzilla.gnome.org/show_bug.cgi?id=768345

 lib/qqwing-wrapper.cpp |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)
---
diff --git a/lib/qqwing-wrapper.cpp b/lib/qqwing-wrapper.cpp
index 3c06312..f659732 100644
--- a/lib/qqwing-wrapper.cpp
+++ b/lib/qqwing-wrapper.cpp
@@ -22,7 +22,9 @@
 #include "qqwing-wrapper.h"
 
 #include <algorithm>
+#include <cstdlib>
 #include <iostream>
+#include <mutex>
 
 #include <glib.h>
 #include <qqwing.hpp>
@@ -37,6 +39,11 @@ int* qqwing_generate_puzzle(int difficulty)
     const int MAX_ITERATIONS = 1000;
     const int BOARD_SIZE = 81;
     qqwing::SudokuBoard board;
+    std::once_flag flag;
+
+    std::call_once(flag, [] {
+        srand(time(nullptr));
+    });
 
     board.setRecordHistory(true);
     board.setLogHistory(false);