More of P0600 - '[[nodiscard]] in the Library' mark empty() as nodiscard in string, string_view, and the free function std::empty(). Removed tabs from <string_view>, which is why the diff is so big.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@318328 91177308-0d34-0410-b5e6-96231b3b80d8

include/iterator

@@ -1791,30 +1791,39 @@ end(const _Cp& __c)
 
 #if _LIBCPP_STD_VER > 14
 template <class _Cont>
+inline _LIBCPP_INLINE_VISIBILITY
 constexpr auto size(const _Cont& __c) -> decltype(__c.size()) { return __c.size(); }
 
 template <class _Tp, size_t _Sz>
+inline _LIBCPP_INLINE_VISIBILITY
 constexpr size_t size(const _Tp (&)[_Sz]) noexcept { return _Sz; }
 
 template <class _Cont>
+_LIBCPP_NODISCARD_AFTER_CXX17 inline _LIBCPP_INLINE_VISIBILITY
 constexpr auto empty(const _Cont& __c) -> decltype(__c.empty()) { return __c.empty(); }
 
 template <class _Tp, size_t _Sz>
+_LIBCPP_NODISCARD_AFTER_CXX17 inline _LIBCPP_INLINE_VISIBILITY
 constexpr bool empty(const _Tp (&)[_Sz]) noexcept { return false; }
 
 template <class _Ep>
+_LIBCPP_NODISCARD_AFTER_CXX17 inline _LIBCPP_INLINE_VISIBILITY
 constexpr bool empty(initializer_list<_Ep> __il) noexcept { return __il.size() == 0; }
 
 template <class _Cont> constexpr
+inline _LIBCPP_INLINE_VISIBILITY
 auto data(_Cont& __c) -> decltype(__c.data()) { return __c.data(); }
 
 template <class _Cont> constexpr
+inline _LIBCPP_INLINE_VISIBILITY
 auto data(const _Cont& __c) -> decltype(__c.data()) { return __c.data(); }
 
 template <class _Tp, size_t _Sz>
+inline _LIBCPP_INLINE_VISIBILITY
 constexpr _Tp* data(_Tp (&__array)[_Sz]) noexcept { return __array; }
 
 template <class _Ep>
+inline _LIBCPP_INLINE_VISIBILITY
 constexpr const _Ep* data(initializer_list<_Ep> __il) noexcept { return __il.begin(); }
 #endif
 

include/string

@@ -901,7 +901,8 @@ public:
     void shrink_to_fit() _NOEXCEPT {reserve();}
     _LIBCPP_INLINE_VISIBILITY
     void clear() _NOEXCEPT;
-    _LIBCPP_INLINE_VISIBILITY bool empty() const _NOEXCEPT {return size() == 0;}
+    _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_INLINE_VISIBILITY
+    bool empty() const _NOEXCEPT {return size() == 0;}
 
     _LIBCPP_INLINE_VISIBILITY const_reference operator[](size_type __pos) const _NOEXCEPT;
     _LIBCPP_INLINE_VISIBILITY reference       operator[](size_type __pos)       _NOEXCEPT;

include/string_view

@@ -263,8 +263,8 @@ public:
     _LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY
     size_type max_size() const _NOEXCEPT { return numeric_limits<size_type>::max(); }
 
-	_LIBCPP_CONSTEXPR bool _LIBCPP_INLINE_VISIBILITY
-	empty()         const _NOEXCEPT { return __size == 0; }
+    _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
+    bool empty()         const _NOEXCEPT { return __size == 0; }
 
     // [string.view.access], element access
     _LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY

test/std/iterators/iterator.container/empty.array.fail.cpp

@@ -0,0 +1,28 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// <iterator>
+
+// <iterator>
+// template <class T, size_t N> constexpr bool empty(const T (&array)[N]) noexcept;
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14, c++17
+// UNSUPPORTED: clang-3.3, clang-3.4, clang-3.5, clang-3.6, clang-3.7, clang-3.8
+
+#include <vector>
+#include <iterator>
+
+#include "test_macros.h"
+
+int main ()
+{
+    int c[5];
+    std::empty(c);  // expected-error {{ignoring return value of function declared with 'nodiscard' attribute}}
+}

test/std/iterators/iterator.container/empty.container.fail.cpp

@@ -0,0 +1,28 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// <iterator>
+
+// <iterator>
+// template <class C> constexpr auto empty(const C& c) -> decltype(c.empty());
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14, c++17
+// UNSUPPORTED: clang-3.3, clang-3.4, clang-3.5, clang-3.6, clang-3.7, clang-3.8
+
+#include <vector>
+#include <iterator>
+
+#include "test_macros.h"
+
+int main ()
+{
+    std::vector<int> c;
+    std::empty(c);  // expected-error {{ignoring return value of function declared with 'nodiscard' attribute}}
+}

test/std/iterators/iterator.container/empty.initializer_list.fail.cpp

@@ -0,0 +1,28 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// <iterator>
+
+// <iterator>
+// template <class E> constexpr bool empty(initializer_list<E> il) noexcept;
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14, c++17
+// UNSUPPORTED: clang-3.3, clang-3.4, clang-3.5, clang-3.6, clang-3.7, clang-3.8
+
+#include <initializer_list>
+#include <iterator>
+
+#include "test_macros.h"
+
+int main ()
+{
+    std::initializer_list<int> c = { 4 };
+    std::empty(c);  // expected-error {{ignoring return value of function declared with 'nodiscard' attribute}}
+}

test/std/strings/basic.string/string.capacity/empty.fail.cpp

@@ -0,0 +1,28 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// <string>
+
+// class deque
+
+// bool empty() const noexcept;
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14, c++17
+// UNSUPPORTED: clang-3.3, clang-3.4, clang-3.5, clang-3.6, clang-3.7, clang-3.8
+
+#include <string>
+
+#include "test_macros.h"
+
+int main ()
+{
+    std::string c;
+    c.empty();  // expected-error {{ignoring return value of function declared with 'nodiscard' attribute}}
+}

test/std/strings/basic.string/string.capacity/empty.pass.cpp

@@ -9,17 +9,19 @@
 
 // <string>
 
-// bool empty() const;
+// bool empty() const noexcept;
 
 #include <string>
 #include <cassert>
 
+#include "test_macros.h"
 #include "min_allocator.h"
 
 template <class S>
 void
 test(const S& s)
 {
+    ASSERT_NOEXCEPT(s.empty());
     assert(s.empty() == (s.size() == 0));
 }
 

test/std/strings/string.view/string.view.capacity/capacity.pass.cpp

@@ -35,6 +35,10 @@ void test1 () {
 
     {
     SV sv1;
+    ASSERT_NOEXCEPT(sv1.size());
+    ASSERT_NOEXCEPT(sv1.empty());
+    ASSERT_NOEXCEPT(sv1.max_size());
+    ASSERT_NOEXCEPT(sv1.length());
     assert ( sv1.size() == 0 );
     assert ( sv1.empty());
     assert ( sv1.size() == sv1.length());

test/std/strings/string.view/string.view.capacity/empty.fail.cpp

@@ -0,0 +1,28 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// <string_view>
+
+// class string_view
+
+// bool empty() const noexcept;
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14, c++17
+// UNSUPPORTED: clang-3.3, clang-3.4, clang-3.5, clang-3.6, clang-3.7, clang-3.8
+
+#include <string_view>
+
+#include "test_macros.h"
+
+int main ()
+{
+    std::string_view c;
+    c.empty();  // expected-error {{ignoring return value of function declared with 'nodiscard' attribute}}
+}