feefrac: avoid integer overflow in temporary

Author: sipa

src/test/feefrac_tests.cpp

@@ -148,6 +148,8 @@ BOOST_AUTO_TEST_CASE(feefrac_operators)
     FeeFrac max_fee2{1, 1};
     BOOST_CHECK(max_fee >= max_fee2);
 
+    // Test for integer overflow issue (https://github.com/bitcoin/bitcoin/issues/32294)
+    BOOST_CHECK_EQUAL((FeeFrac{0x7ffffffdfffffffb, 0x7ffffffd}.EvaluateFeeDown(0x7fffffff)), 0x7fffffffffffffff);
 }
 
 BOOST_AUTO_TEST_SUITE_END()

src/util/feefrac.h

@@ -96,7 +96,7 @@ struct FeeFrac
         int64_t quot = n / d;
         int32_t mod = n % d;
         // Correct result if the / operator above rounded in the wrong direction.
-        return quot + (mod > 0) - (mod && round_down);
+        return quot + ((mod > 0) - (mod && round_down));
     }
 #else
     static constexpr auto Mul = MulFallback;