Fix [damage] weapon special produces unexpected damage values

Fix wesnoth#9467

data/test/scenarios/wml_tests/UnitsWML/AbilitiesWML/special_calculations.cfg

@@ -178,9 +178,9 @@
 # API(s) being tested: [attacks]divide=
 ##
 # Expected end state:
-# Bob's attack has 4 strikes after rounding down.
+# Bob's attack has 5 strikes after rounding up.
 #####
-{ONE_CALCULATION_UNIT_TEST divide_float_2dp 10 (divide=2.02) 4}
+{ONE_CALCULATION_UNIT_TEST divide_float_2dp 10 (divide=2.02) 5}
 #####
 # API(s) being tested: [attacks]divide=
 ##
@@ -192,16 +192,16 @@
 # API(s) being tested: [attacks]
 ##
 # Expected end state:
-# Bob's attack is the expected answer: 10 strikes * 2 / 3 = 6 strikes after rounding down.
+# Bob's attack is the expected answer: 10 strikes * 2 / 3 = 7 strikes after rounding up.
 #####
-{ONE_CALCULATION_UNIT_TEST divide_multiply_combined 10 (divide,multiply=3,2) 6}
+{ONE_CALCULATION_UNIT_TEST divide_multiply_combined 10 (divide,multiply=3,2) 7}
 #####
 # API(s) being tested: [attacks]divide=,[attacks]multiply=
 ##
 # Expected end state:
-# Bob's attack is the expected answer: 10 strikes * 2 / 3 = 6 strikes after rounding down.
+# Bob's attack is the expected answer: 10 strikes * 2 / 3 = 7 strikes after rounding up.
 #####
-{TWO_CALCULATION_UNIT_TEST divide_multiply_separated 10 (divide=3) (multiply=2) 6}
+{TWO_CALCULATION_UNIT_TEST divide_multiply_separated 10 (divide=3) (multiply=2) 7}
 #####
 # API(s) being tested: [attacks]multiply=
 ##
@@ -213,9 +213,9 @@
 # API(s) being tested: [attacks]multiply=
 ##
 # Expected end state:
-# Bob's attack has 9 strikes, because 3 * 3.334 first rounds 3.334 to 3.33, and then 3 * 3.33 floors to 9.
+# Bob's attack has 10 strikes, because 3 * 3.334 first rounds 3.334 to 3.33, and then 3 * 3.33 floors to 10.
 #####
-{ONE_CALCULATION_UNIT_TEST multiply_float_3dp 3 (multiply=3.334) 9}
+{ONE_CALCULATION_UNIT_TEST multiply_float_3dp 3 (multiply=3.334) 10}
 
 #undef ONE_CALCULATION_UNIT_TEST
 #undef TWO_CALCULATION_UNIT_TEST

src/units/abilities.cpp

@@ -2474,7 +2474,11 @@ effect::effect(const unit_ability_list& list, int def, const_attack_ptr att, EFF
 		effect_list_.push_back(val.second);
 	}
 
-	composite_value_ = static_cast<int>((value_set + addition + substraction) * multiplier / divisor);
+	double temp_value = (value_set + addition + substraction) * multiplier / divisor;
+	composite_value_ = static_cast<int>(temp_value);
+	if((temp_value - composite_value_) >= 0.5){
+		composite_value_ = std::round(temp_value);
+	}
 	//clamp what if min_value < max_value or one attribute only used.
 	if(max_value && min_value && *min_value < *max_value) {
 		composite_value_ = std::clamp(*min_value, *max_value, composite_value_);