Make lcm/gcd work better in edge cases. Fixes a UBSAN failure.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@294779 91177308-0d34-0410-b5e6-96231b3b80d8
2017-02-10 20:49:08 +00:00
parent 00d9a944af
commit ebf66a385f
6 changed files with 52 additions and 28 deletions
--- a/test/std/experimental/numeric/numeric.ops/numeric.ops.gcd/gcd.pass.cpp
+++ b/test/std/experimental/numeric/numeric.ops/numeric.ops.gcd/gcd.pass.cpp
@@ -129,4 +129,11 @@ int main()
    assert((do_test<long, int>(non_cce)));
    assert((do_test<int, long long>(non_cce)));
    assert((do_test<long long, int>(non_cce)));
+
+//  LWG#2792
+    {
+        auto res = std::gcd((int64_t)1234, (int32_t)-2147483648);
+        static_assert( std::is_same<decltype(res), std::common_type<int64_t, int32_t>::type>::value, "");
+        assert(res == 2);
+    }
 }