More of P0600 - '[[nodiscard]] in the Library' mark empty() as nodiscard in match_results. <regex>

llvm-svn: 318375

2 files changed, 31 insertions, 4 deletions

diff --git a/libcxx/include/regex b/libcxx/include/regex
index 553d08d8188..ff84b2738b7 100644
--- a/libcxx/include/regex
+++ b/libcxx/include/regex
@@ -5240,11 +5240,11 @@ public:
 
     // size:
     _LIBCPP_INLINE_VISIBILITY
-    size_type size() const {return __matches_.size();}
+    size_type size() const _NOEXCEPT {return __matches_.size();}
     _LIBCPP_INLINE_VISIBILITY
-    size_type max_size() const {return __matches_.max_size();}
-    _LIBCPP_INLINE_VISIBILITY
-    bool empty() const {return size() == 0;}
+    size_type max_size() const _NOEXCEPT {return __matches_.max_size();}
+    _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_INLINE_VISIBILITY
+    bool empty() const _NOEXCEPT {return size() == 0;}
 
     // element access:
     _LIBCPP_INLINE_VISIBILITY
diff --git a/libcxx/test/std/re/re.results/re.results.size/empty.fail.cpp b/libcxx/test/std/re/re.results/re.results.size/empty.fail.cpp
new file mode 100644
index 00000000000..6f677f3907a
--- /dev/null
+++ b/libcxx/test/std/re/re.results/re.results.size/empty.fail.cpp
@@ -0,0 +1,27 @@
+// -*- 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.
+//
+//===----------------------------------------------------------------------===//
+
+// <regex>
+
+// class match_results<BidirectionalIterator, Allocator>
+// bool empty() const;
+
+// 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 <regex>
+
+#include "test_macros.h"
+
+int main ()
+{
+    std::match_results<const char*> c;
+    c.empty();  // expected-error {{ignoring return value of function declared with 'nodiscard' attribute}}
+}