cpp/openttd-patchpack/source Changeset - r25890:31b085404537

Changeset - r25890:31b085404537

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Michael Lutz - 3 years ago 2021-08-15 10:14:53
michi@icosahedron.de

Fix 2183fd4d: [NewGRF] Use divide instead of right shift for signed numbers. (#9480)

"For negative a, the value of a >> b is implementation-defined (in most implementations, this performs arithmetic right shift, so that the result remains negative)."

2 files changed with 2 insertions and 2 deletions:

src/newgrf_engine.cpp

src/train_cmd.cpp

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src/newgrf_engine.cpp

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@@ @@ -1186,13 +1186,13 @@ int GetVehicleProperty(const Vehicle *v, @@
 int GetEngineProperty(EngineID engine, PropertyID property, int orig_value, const Vehicle *v, bool is_signed)
+{
 	uint16 callback = GetVehicleCallback(CBID_VEHICLE_MODIFY_PROPERTY, property, 0, engine, v);
 	if (callback != CALLBACK_FAILED) {
 		if (is_signed) {
 			/* Sign extend 15 bit integer */
-			return static_cast<int16>(callback << 1) >> 1;
+			return static_cast<int16>(callback << 1) / 2;
 		} else {
 			return callback;
+		}
+	}
 	return orig_value;

src/train_cmd.cpp

➞

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@@ @@ -360,13 +360,13 @@ int Train::GetCurveSpeedLimit() const @@
 			/* Apply max_speed bonus of 20% for a tilting train */
 			max_speed += max_speed / 5;
+		}
 		/* Apply max_speed modifier (cached value is fixed-point binary with 8 fractional bits)
 		 * and clamp the result to an acceptable range. */
-		max_speed += (max_speed * this->tcache.cached_curve_speed_mod) >> 8;
+		max_speed += (max_speed * this->tcache.cached_curve_speed_mod) / 256;
 		max_speed = Clamp(max_speed, 2, absolute_max_speed);
+	}
 	return max_speed;
+}

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