Added a new macro BOOST_EXPLICIT_OPERATOR_BOOL_NOEXCEPT, which implements a noexcept operator. Also added explicit noexcept specification for the constexpr macro.

doc/explicit_operator_bool.qbk

@@ -5,7 +5,7 @@
  / file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  /]
 
-[article BOOST_EXPLICIT_OPERATOR_BOOL and BOOST_CONSTEXPR_EXPLICIT_OPERATOR_BOOL
+[article BOOST_EXPLICIT_OPERATOR_BOOL, BOOST_EXPLICIT_OPERATOR_BOOL_NOEXCEPT and BOOST_CONSTEXPR_EXPLICIT_OPERATOR_BOOL
     [quickbook 1.5]
     [authors [Semashev, Andrey]]
     [copyright 2013 Andrey Semashev]
@@ -20,7 +20,7 @@
 [section Overview]
 [/===============]
 
-`BOOST_EXPLICIT_OPERATOR_BOOL()` and `BOOST_CONSTEXPR_EXPLICIT_OPERATOR_BOOL()` are compatibility helper macros that expand to an explicit conversion operator to `bool`. For compilers not supporting explicit conversion operators introduced in C++11 the macros expand to a conversion operator that implements the [@http://en.wikibooks.org/wiki/More_C%2B%2B_Idioms/Safe_bool safe bool idiom]. In case if the compiler is not able to handle safe bool idiom well the macros expand to a regular conversion operator to `bool`.
+`BOOST_EXPLICIT_OPERATOR_BOOL()`, `BOOST_EXPLICIT_OPERATOR_BOOL_NOEXCEPT()` and `BOOST_CONSTEXPR_EXPLICIT_OPERATOR_BOOL()` are compatibility helper macros that expand to an explicit conversion operator to `bool`. For compilers not supporting explicit conversion operators introduced in C++11 the macros expand to a conversion operator that implements the [@http://en.wikibooks.org/wiki/More_C%2B%2B_Idioms/Safe_bool safe bool idiom]. In case if the compiler is not able to handle safe bool idiom well the macros expand to a regular conversion operator to `bool`.
 
 [endsect]
 
@@ -62,7 +62,3 @@ Now `my_ptr` can be used in conditional expressions, similarly to a regular poin
 * The macro was extracted from Boost.Log.
 
 [endsect]
-
-
-
-

include/boost/utility/explicit_operator_bool.hpp

@@ -38,6 +38,19 @@
         return !this->operator! ();\
     }
 
+/*!
+ * \brief The macro defines a noexcept explicit operator of conversion to \c bool
+ *
+ * The macro should be used inside the definition of a class that has to
+ * support the conversion. The class should also implement <tt>operator!</tt>,
+ * in terms of which the conversion operator will be implemented.
+ */
+#define BOOST_EXPLICIT_OPERATOR_BOOL_NOEXCEPT()\
+    BOOST_FORCEINLINE explicit operator bool () const BOOST_NOEXCEPT\
+    {\
+        return !this->operator! ();\
+    }
+
 /*!
  * \brief The macro defines a constexpr explicit operator of conversion to \c bool
  *
@@ -46,7 +59,7 @@
  * in terms of which the conversion operator will be implemented.
  */
 #define BOOST_CONSTEXPR_EXPLICIT_OPERATOR_BOOL()\
-    BOOST_FORCEINLINE BOOST_CONSTEXPR explicit operator bool () const\
+    BOOST_FORCEINLINE BOOST_CONSTEXPR explicit operator bool () const BOOST_NOEXCEPT\
     {\
         return !this->operator! ();\
     }
@@ -101,8 +114,14 @@ namespace detail {
         return (!this->operator! () ? &boost::detail::unspecified_bool::true_value : (boost::detail::unspecified_bool_type)0);\
     }
 
+#define BOOST_EXPLICIT_OPERATOR_BOOL_NOEXCEPT()\
+    BOOST_FORCEINLINE operator boost::detail::unspecified_bool_type () const BOOST_NOEXCEPT\
+    {\
+        return (!this->operator! () ? &boost::detail::unspecified_bool::true_value : (boost::detail::unspecified_bool_type)0);\
+    }
+
 #define BOOST_CONSTEXPR_EXPLICIT_OPERATOR_BOOL()\
-    BOOST_FORCEINLINE BOOST_CONSTEXPR operator boost::detail::unspecified_bool_type () const\
+    BOOST_FORCEINLINE BOOST_CONSTEXPR operator boost::detail::unspecified_bool_type () const BOOST_NOEXCEPT\
     {\
         return (!this->operator! () ? &boost::detail::unspecified_bool::true_value : (boost::detail::unspecified_bool_type)0);\
     }
@@ -115,8 +134,14 @@ namespace detail {
         return !this->operator! ();\
     }
 
+#define BOOST_EXPLICIT_OPERATOR_BOOL()\
+    BOOST_FORCEINLINE operator bool () const BOOST_NOEXCEPT\
+    {\
+        return !this->operator! ();\
+    }
+
 #define BOOST_CONSTEXPR_EXPLICIT_OPERATOR_BOOL()\
-    BOOST_FORCEINLINE BOOST_CONSTEXPR operator bool () const\
+    BOOST_FORCEINLINE BOOST_CONSTEXPR operator bool () const BOOST_NOEXCEPT\
     {\
         return !this->operator! ();\
     }

index.html

@@ -34,7 +34,7 @@
 				<a href="utility.htm">utility</a><br>
             <a href="doc/html/string_ref.html">string_ref</a><br>
             <a href="value_init.htm">value_init</a><br>
-            <a href="doc/html/explicit_operator_bool.html">BOOST_EXPLICIT_OPERATOR_BOOL and BOOST_CONSTEXPR_EXPLICIT_OPERATOR_BOOL</a>
+            <a href="doc/html/explicit_operator_bool.html">BOOST_EXPLICIT_OPERATOR_BOOL, BOOST_EXPLICIT_OPERATOR_BOOL_NOEXCEPT and BOOST_CONSTEXPR_EXPLICIT_OPERATOR_BOOL</a>
          </p>
 		</blockquote>
 		<hr>

test/Jamfile.v2

@@ -47,6 +47,7 @@ test-suite utility
         [ compile-fail ../initialized_test_fail1.cpp ]
         [ compile-fail ../initialized_test_fail2.cpp ]
         [ run explicit_operator_bool.cpp ]
+        [ run explicit_operator_bool_noexcept.cpp ]
         [ compile-fail explicit_operator_bool_compile_fail_conv_int.cpp ]
         [ compile-fail explicit_operator_bool_compile_fail_conv_pvoid.cpp ]
         [ compile-fail explicit_operator_bool_compile_fail_delete.cpp ]

test/explicit_operator_bool.cpp

@@ -5,7 +5,7 @@
  *          http://www.boost.org/LICENSE_1_0.txt)
  */
 /*!
- * \file   explicit_operator_bool_compile.cpp
+ * \file   explicit_operator_bool.cpp
  * \author Andrey Semashev
  * \date   17.07.2010
  *
@@ -13,7 +13,7 @@
  *         the valid contexts.
  */
 
-#define BOOST_TEST_MODULE explicit_operator_bool_compile
+#define BOOST_TEST_MODULE explicit_operator_bool
 
 #include <boost/utility/explicit_operator_bool.hpp>
 

test/explicit_operator_bool_noexcept.cpp

@@ -0,0 +1,89 @@
+/*
+ *          Copyright Andrey Semashev 2007 - 2013.
+ * Distributed under the Boost Software License, Version 1.0.
+ *    (See accompanying file LICENSE_1_0.txt or copy at
+ *          http://www.boost.org/LICENSE_1_0.txt)
+ */
+/*!
+ * \file   explicit_operator_bool_noexcept.cpp
+ * \author Andrey Semashev
+ * \date   26.04.2014
+ *
+ * \brief  This test checks that explicit operator bool is noexcept when possible.
+ */
+
+#define BOOST_TEST_MODULE explicit_operator_bool_noexcept
+
+#include <boost/config.hpp>
+
+#if !defined(BOOST_NO_CXX11_NOEXCEPT)
+
+#include <boost/detail/lightweight_test.hpp>
+#include <boost/utility/explicit_operator_bool.hpp>
+
+namespace {
+
+    struct checkable1
+    {
+        BOOST_EXPLICIT_OPERATOR_BOOL()
+        bool operator! () const
+        {
+            return false;
+        }
+    };
+
+    struct checkable2
+    {
+        BOOST_CONSTEXPR_EXPLICIT_OPERATOR_BOOL()
+        BOOST_CONSTEXPR bool operator! () const
+        {
+            return false;
+        }
+    };
+
+    struct noexcept_checkable1
+    {
+        BOOST_EXPLICIT_OPERATOR_BOOL_NOEXCEPT()
+        bool operator! () const noexcept
+        {
+            return false;
+        }
+    };
+
+    struct noexcept_checkable2
+    {
+        BOOST_CONSTEXPR_EXPLICIT_OPERATOR_BOOL()
+        BOOST_CONSTEXPR bool operator! () const noexcept
+        {
+            return false;
+        }
+    };
+
+} // namespace
+
+int main(int, char*[])
+{
+    checkable1 val1;
+    checkable2 val2;
+
+    noexcept_checkable1 noexcept_val1;
+    noexcept_checkable2 noexcept_val2;
+
+    BOOST_TEST(!noexcept(static_cast< bool >(val1)));
+    // constexpr functions are implicitly noexcept
+    BOOST_TEST(noexcept(static_cast< bool >(val2)));
+
+    BOOST_TEST(noexcept(static_cast< bool >(noexcept_val1)));
+    BOOST_TEST(noexcept(static_cast< bool >(noexcept_val2)));
+
+    return boost::report_errors();
+}
+
+#else
+
+int main(int, char*[])
+{
+    return 0;
+}
+
+#endif