Replaced use of std::rand with std::mt19937

This uses a global instance of the RNG

include/internal/catch_random_number_generator.cpp

@@ -9,23 +9,21 @@
 #include "catch_context.h"
 #include "catch_interfaces_config.h"
 
-#include <cstdlib>
-
 namespace Catch {
 
-    void seedRng( IConfig const& config ) {
-        if( config.rngSeed() != 0 )
-            std::srand( config.rngSeed() );
+    std::mt19937& rng() {
+        static std::mt19937 s_rng;
+        return s_rng;
     }
+
+    void seedRng( IConfig const& config ) {
+        if( config.rngSeed() != 0 ) {
+            std::srand( config.rngSeed() );
+            rng().seed( config.rngSeed() );
+        }
+    }
+
     unsigned int rngSeed() {
         return getCurrentContext().getConfig()->rngSeed();
     }
-
-    RandomNumberGenerator::result_type RandomNumberGenerator::operator()( result_type n ) const {
-        return std::rand() % n;
-    }
-    RandomNumberGenerator::result_type RandomNumberGenerator::operator()() const {
-        return std::rand() % (max)();
-    }
-
 }

include/internal/catch_random_number_generator.h

@@ -8,31 +8,16 @@
 #define TWOBLUECUBES_CATCH_RANDOM_NUMBER_GENERATOR_H_INCLUDED
 
 #include <algorithm>
+#include <random>
 
 namespace Catch {
 
     struct IConfig;
 
+    std::mt19937& rng();
     void seedRng( IConfig const& config );
-
     unsigned int rngSeed();
 
-    struct RandomNumberGenerator {
-        using result_type = unsigned int;
-
-        static constexpr result_type (min)() { return 0; }
-        static constexpr result_type (max)() { return 1000000; }
-
-        result_type operator()( result_type n ) const;
-        result_type operator()() const;
-
-        template<typename V>
-        static void shuffle( V& vector ) {
-            RandomNumberGenerator rng;
-            std::shuffle( vector.begin(), vector.end(), rng );
-        }
-    };
-
 }
 
 #endif // TWOBLUECUBES_CATCH_RANDOM_NUMBER_GENERATOR_H_INCLUDED

include/internal/catch_test_case_registry_impl.cpp

@@ -28,7 +28,7 @@ namespace Catch {
                 break;
             case RunTests::InRandomOrder:
                 seedRng( config );
-                RandomNumberGenerator::shuffle( sorted );
+                std::shuffle( sorted.begin(), sorted.end(), rng() );
                 break;
             case RunTests::InDeclarationOrder:
                 // already in declaration order