3 files changed, 58 insertions, 2 deletions
diff --git a/src/mapgen/mapgen.cpp b/src/mapgen/mapgen.cpp
index d767bd264..1f2ac491e 100644
--- a/src/mapgen/mapgen.cpp
+++ b/src/mapgen/mapgen.cpp
@@ -238,7 +238,8 @@ u32 Mapgen::getBlockSeed(v3s16 p, s32 seed)
 
 u32 Mapgen::getBlockSeed2(v3s16 p, s32 seed)
 {
-	u32 n = 1619 * p.X + 31337 * p.Y + 52591 * p.Z + 1013 * seed;
+	// Multiply by unsigned number to avoid signed overflow (UB)
+	u32 n = 1619U * p.X + 31337U * p.Y + 52591U * p.Z + 1013U * seed;
 	n = (n >> 13) ^ n;
 	return (n * (n * n * 60493 + 19990303) + 1376312589);
 }
diff --git a/src/noise.cpp b/src/noise.cpp
index 2f4de6855..d98d4dafb 100644
--- a/src/noise.cpp
+++ b/src/noise.cpp
@@ -35,7 +35,8 @@
 #define NOISE_MAGIC_X    1619
 #define NOISE_MAGIC_Y    31337
 #define NOISE_MAGIC_Z    52591
-#define NOISE_MAGIC_SEED 1013
+// Unsigned magic seed prevents undefined behavior.
+#define NOISE_MAGIC_SEED 1013U
 
 typedef float (*Interp2dFxn)(
 		float v00, float v10, float v01, float v11,
diff --git a/src/unittest/test_noise.cpp b/src/unittest/test_noise.cpp
index 421f3b66e..12b155f46 100644
--- a/src/unittest/test_noise.cpp
+++ b/src/unittest/test_noise.cpp
@@ -30,8 +30,14 @@ public:
 
 	void runTests(IGameDef *gamedef);
 
+	void testNoise2dAtOriginWithZeroSeed();
+	void testNoise2dWithMaxSeed();
+	void testNoise2dWithFunPrimes();
 	void testNoise2dPoint();
 	void testNoise2dBulk();
+	void testNoise3dAtOriginWithZeroSeed();
+	void testNoise3dWithMaxSeed();
+	void testNoise3dWithFunPrimes();
 	void testNoise3dPoint();
 	void testNoise3dBulk();
 	void testNoiseInvalidParams();
@@ -44,8 +50,14 @@ static TestNoise g_test_instance;
 
 void TestNoise::runTests(IGameDef *gamedef)
 {
+	TEST(testNoise2dAtOriginWithZeroSeed);
+	TEST(testNoise2dWithMaxSeed);
+	TEST(testNoise2dWithFunPrimes);
 	TEST(testNoise2dPoint);
 	TEST(testNoise2dBulk);
+	TEST(testNoise3dAtOriginWithZeroSeed);
+	TEST(testNoise3dWithMaxSeed);
+	TEST(testNoise3dWithFunPrimes);
 	TEST(testNoise3dPoint);
 	TEST(testNoise3dBulk);
 	TEST(testNoiseInvalidParams);
@@ -53,6 +65,27 @@ void TestNoise::runTests(IGameDef *gamedef)
 
 ////////////////////////////////////////////////////////////////////////////////
 
+void TestNoise::testNoise2dAtOriginWithZeroSeed()
+{
+	float actual{ noise2d(0, 0, 0) };
+	constexpr float expected{ -0.281791f };
+	UASSERT(std::fabs(actual - expected) <= 0.00001);
+}
+
+void TestNoise::testNoise2dWithMaxSeed()
+{
+	float actual{ noise2d(4096, 4096, 2147483647) };
+	constexpr float expected{ 0.950606f };
+	UASSERT(std::fabs(actual - expected) <= 0.00001);
+}
+
+void TestNoise::testNoise2dWithFunPrimes()
+{
+	float actual{ noise2d(-3947, -2333, 7027) };
+	constexpr float expected{ -0.294907f };
+	UASSERT(std::fabs(actual - expected) <= 0.00001);
+}
+
 void TestNoise::testNoise2dPoint()
 {
 	NoiseParams np_normal(20, 40, v3f(50, 50, 50), 9,  5, 0.6, 2.0);
@@ -79,6 +112,27 @@ void TestNoise::testNoise2dBulk()
 	}
 }
 
+void TestNoise::testNoise3dAtOriginWithZeroSeed()
+{
+	float actual{ noise2d(0, 0, 0) };
+	constexpr float expected{ -0.281791f };
+	UASSERT(std::fabs(actual - expected) <= 0.00001);
+}
+
+void TestNoise::testNoise3dWithMaxSeed()
+{
+	float actual{ noise3d(4096, 4096, 4096, 2147483647) };
+	constexpr float expected{ -0.775243f };
+	UASSERT(std::fabs(actual - expected) <= 0.00001);
+}
+
+void TestNoise::testNoise3dWithFunPrimes()
+{
+	float actual{ noise2d(3903, -1723, 7411) };
+	constexpr float expected{ 0.989124f };
+	UASSERT(std::fabs(actual - expected) <= 0.00001);
+}
+
 void TestNoise::testNoise3dPoint()
 {
 	NoiseParams np_normal(20, 40, v3f(50, 50, 50), 9,  5, 0.6, 2.0);