std::abs isn't suitable for these functions because we need something
that works in constexpr functions and with unsigned types.
Also, <experimental/numeric> is supposed to include <numeric>.
PR libstdc++/77801
* include/experimental/numeric: Include <numeric>.
(__abs): Define.
(gcd, lcm): Use __abs instead of std::abs.
* testsuite/experimental/numeric/77801.cc: New test.
* testsuite/experimental/numeric/gcd.cc: Test unsigned inputs.
* testsuite/experimental/numeric/lcm.cc: Likewise.
Tested powerpc64le-linux, committed to trunk. Backport to gcc-6
coming too.
commit 49396c6b134c5994e6a7e5dff766dc8cf1290dc1
Author: Jonathan Wakely <jwak...@redhat.com>
Date: Fri Sep 30 14:20:10 2016 +0100
Remove use of std::abs in experimental::{gcd,lcm}
PR libstdc++/77801
* include/experimental/numeric: Include <numeric>.
(__abs): Define.
(gcd, lcm): Use __abs instead of std::abs.
* testsuite/experimental/numeric/77801.cc: New test.
* testsuite/experimental/numeric/gcd.cc: Test unsigned inputs.
* testsuite/experimental/numeric/lcm.cc: Likewise.
diff --git a/libstdc++-v3/include/experimental/numeric
b/libstdc++-v3/include/experimental/numeric
index 21878f3..5089772 100644
--- a/libstdc++-v3/include/experimental/numeric
+++ b/libstdc++-v3/include/experimental/numeric
@@ -39,8 +39,8 @@
# include <bits/c++14_warning.h>
#else
+#include <numeric>
#include <experimental/type_traits>
-#include <cmath>
namespace std _GLIBCXX_VISIBILITY(default)
{
@@ -52,6 +52,19 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
#define __cpp_lib_experimental_gcd_lcm 201411
+ // std::abs is not constexpr and doesn't support unsigned integers.
+ template<typename _Tp>
+ constexpr
+ enable_if_t<__and_<is_integral<_Tp>, is_signed<_Tp>>::value, _Tp>
+ __abs(_Tp __val)
+ { return __val < 0 ? -__val : __val; }
+
+ template<typename _Tp>
+ constexpr
+ enable_if_t<__and_<is_integral<_Tp>, is_unsigned<_Tp>>::value, _Tp>
+ __abs(_Tp __val)
+ { return __val; }
+
// Greatest common divisor
template<typename _Mn, typename _Nn>
constexpr common_type_t<_Mn, _Nn>
@@ -60,8 +73,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
static_assert(is_integral<_Mn>::value, "arguments to gcd are integers");
static_assert(is_integral<_Nn>::value, "arguments to gcd are integers");
- return __m == 0 ? std::abs(__n)
- : __n == 0 ? std::abs(__m)
+ return __m == 0 ? fundamentals_v2::__abs(__n)
+ : __n == 0 ? fundamentals_v2::__abs(__m)
: fundamentals_v2::gcd(__n, __m % __n);
}
@@ -74,7 +87,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
static_assert(is_integral<_Nn>::value, "arguments to lcm are integers");
return (__m != 0 && __n != 0)
- ? (std::abs(__m) / fundamentals_v2::gcd(__m, __n)) * std::abs(__n)
+ ? (fundamentals_v2::__abs(__m) / fundamentals_v2::gcd(__m, __n))
+ * fundamentals_v2::__abs(__n)
: 0;
}
diff --git a/libstdc++-v3/testsuite/experimental/numeric/77801.cc
b/libstdc++-v3/testsuite/experimental/numeric/77801.cc
new file mode 100644
index 0000000..c4c8bfb
--- /dev/null
+++ b/libstdc++-v3/testsuite/experimental/numeric/77801.cc
@@ -0,0 +1,22 @@
+// Copyright (C) 2016 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library. This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3. If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-do compile { target c++14 } }
+
+#include <cstdlib>
+#include <experimental/numeric>
+constexpr int i = std::experimental::gcd(4L, 5L); // PR libstdc++/77801
diff --git a/libstdc++-v3/testsuite/experimental/numeric/gcd.cc
b/libstdc++-v3/testsuite/experimental/numeric/gcd.cc
index 038f12d..b3345dc 100644
--- a/libstdc++-v3/testsuite/experimental/numeric/gcd.cc
+++ b/libstdc++-v3/testsuite/experimental/numeric/gcd.cc
@@ -25,3 +25,7 @@ static_assert(lcm(21, 6) == 42, "");
static_assert(lcm(41, 0) == 0, "LCD with zero is zero");
static_assert(lcm(0, 7) == 0, "LCD with zero is zero");
static_assert(lcm(0, 0) == 0, "no division by zero");
+
+static_assert(lcm(1u, 2) == 2, "unsigned and signed");
+static_assert(lcm(3, 4u) == 12, "signed and unsigned");
+static_assert(lcm(5u, 6u) == 30, "unsigned and unsigned");
diff --git a/libstdc++-v3/testsuite/experimental/numeric/lcm.cc
b/libstdc++-v3/testsuite/experimental/numeric/lcm.cc
index 2c969b0..d90c152 100644
--- a/libstdc++-v3/testsuite/experimental/numeric/lcm.cc
+++ b/libstdc++-v3/testsuite/experimental/numeric/lcm.cc
@@ -29,3 +29,6 @@ static_assert( gcd(0, 13) == 13, "GCD of any number and 0 is
that number" );
static_assert( gcd(29, 0) == 29, "GCD of any number and 0 is that number" );
static_assert( gcd(0, 0) == 0, "" );
+static_assert(gcd(1u, 2) == 1, "unsigned and signed");
+static_assert(gcd(3, 4u) == 1, "signed and unsigned");
+static_assert(gcd(5u, 6u) == 1, "unsigned and unsigned");
