Fix -Wdouble-promotion warnings.

Reviewers: mclow.lists

Subscribers: christof, ldionne, cfe-commits, libcxx-commits

Differential Revision: https://reviews.llvm.org/D62782

llvm-svn: 364798
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: ba41d3b1fd68ce1efa467df93e6a22faa277a944
diff --git a/include/limits b/include/limits
index 82c1ea1..6d5d1e1 100644
--- a/include/limits
+++ b/include/limits
@@ -409,7 +409,7 @@
     static _LIBCPP_CONSTEXPR const bool is_exact = false;
     static _LIBCPP_CONSTEXPR const int  radix = __FLT_RADIX__;
     _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR type epsilon() _NOEXCEPT {return __LDBL_EPSILON__;}
-    _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR type round_error() _NOEXCEPT {return 0.5;}
+    _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR type round_error() _NOEXCEPT {return 0.5L;}
 
     static _LIBCPP_CONSTEXPR const int  min_exponent = __LDBL_MIN_EXP__;
     static _LIBCPP_CONSTEXPR const int  min_exponent10 = __LDBL_MIN_10_EXP__;