diff options
| author | Wladimir J. van der Laan <laanwj@gmail.com> | 2018-04-09 05:50:26 +0200 |
|---|---|---|
| committer | Wladimir J. van der Laan <laanwj@gmail.com> | 2018-04-09 05:57:19 +0200 |
| commit | 4781813b56177f8cfc1bf3d4160f75f3ec15e7e2 (patch) | |
| tree | e76f7df8fb6bdd8682ad315b590878238694569c | |
| parent | 27278dffe877ab95488f2e0fada53edb9590487f (diff) | |
| parent | b120f7bdbee83c00e46a9ec6d0cd09a816631f45 (diff) | |
Merge #12537: [arith_uint256] Make it safe to use "self" in operators
b120f7b [test] Add tests for self usage in arith_uint256 (Karl-Johan Alm)
08b17de [arith_uint256] Do not destroy *this content if passed-in operator may reference it (Karl-Johan Alm)
Pull request description:
Before this fix (see test commit), `v *= v` would result in `0` because `operator*=` set `*this` (`==b`) to `0` at the start. This patch changes the code to use `a` as temporary for `*this`~~, with drawback that `*this` is set to `a` at the end, an extra `=` operation in other words~~.
Tree-SHA512: 8028a99880c3198a39c4bcc5056169735ba960625d553e15c0317510a52940c875f7a1fefe14e1af7fcf10c07a246411994a328cb1507bf3eaf1b6e7425390dc
| -rw-r--r-- | src/arith_uint256.cpp | 8 | ||||
| -rw-r--r-- | src/test/uint256_tests.cpp | 13 |
2 files changed, 17 insertions, 4 deletions
diff --git a/src/arith_uint256.cpp b/src/arith_uint256.cpp index 65de632306..c7ddb17eb0 100644 --- a/src/arith_uint256.cpp +++ b/src/arith_uint256.cpp @@ -69,16 +69,16 @@ base_uint<BITS>& base_uint<BITS>::operator*=(uint32_t b32) template <unsigned int BITS> base_uint<BITS>& base_uint<BITS>::operator*=(const base_uint& b) { - base_uint<BITS> a = *this; - *this = 0; + base_uint<BITS> a; for (int j = 0; j < WIDTH; j++) { uint64_t carry = 0; for (int i = 0; i + j < WIDTH; i++) { - uint64_t n = carry + pn[i + j] + (uint64_t)a.pn[j] * b.pn[i]; - pn[i + j] = n & 0xffffffff; + uint64_t n = carry + a.pn[i + j] + (uint64_t)pn[j] * b.pn[i]; + a.pn[i + j] = n & 0xffffffff; carry = n >> 32; } } + *this = a; return *this; } diff --git a/src/test/uint256_tests.cpp b/src/test/uint256_tests.cpp index ad5478e829..20ed29f59b 100644 --- a/src/test/uint256_tests.cpp +++ b/src/test/uint256_tests.cpp @@ -266,4 +266,17 @@ BOOST_AUTO_TEST_CASE( conversion ) BOOST_CHECK(R2L.GetHex() == UintToArith256(R2L).GetHex()); } +BOOST_AUTO_TEST_CASE( operator_with_self ) +{ + arith_uint256 v = UintToArith256(uint256S("02")); + v *= v; + BOOST_CHECK(v == UintToArith256(uint256S("04"))); + v /= v; + BOOST_CHECK(v == UintToArith256(uint256S("01"))); + v += v; + BOOST_CHECK(v == UintToArith256(uint256S("02"))); + v -= v; + BOOST_CHECK(v == UintToArith256(uint256S("0"))); +} + BOOST_AUTO_TEST_SUITE_END() |