Enable usage of gsl::narrow with exceptions disabled (#640)v1.0.0

* Enable usage of gsl::narrow with exceptions disabled

This solution uses the approach of boost::asio to enabling usage of the
library in environments where exception usage is either prohibited
or not feasible (due to code size constraints). A function template
gsl::throw_exception has been added, which in a normal environment just
throws the exception. However, when GSL_TERMINATE_ON_CONTRACT_VIOLATION
is defined the function is only declared by gsl and the definition of
this function template must be supplied by the library's user.

Closes: #468

Signed-off-by: Damian Jarek <damian.jarek93@gmail.com>

Addition:
- understand STL no exception macro
- use function static variable to set termination handler in kernel mode
- add compile-only tests for no-exception mode

* added termination tests and fixed bugs

* disabled warning C4577 for msvc 2015

5 files changed, 223 insertions, 6 deletions

diff --git a/include/gsl/gsl_assert b/include/gsl/gsl_assert
index eeb3473..2bda149 100644
--- a/include/gsl/gsl_assert
+++ b/include/gsl/gsl_assert
@@ -21,6 +21,14 @@
 #include <stdexcept> // for logic_error
 
 //
+// Temporary until MSVC STL supports no-exceptions mode.
+// Currently terminate is a no-op in this mode, so we add termination behavior back
+//
+#if defined(_MSC_VER) && defined(_HAS_EXCEPTIONS) && !_HAS_EXCEPTIONS
+#define GSL_MSVC_USE_STL_NOEXCEPTION_WORKAROUND
+#endif
+
+//
 // There are three configuration options for this GSL implementation's behavior
 // when pre/post conditions on the GSL types are violated:
 //
@@ -68,18 +76,62 @@ struct fail_fast : public std::logic_error
 {
     explicit fail_fast(char const* const message) : std::logic_error(message) {}
 };
-}
+
+namespace details
+{
+#if defined(GSL_MSVC_USE_STL_NOEXCEPTION_WORKAROUND)
+
+    typedef void  (*terminate_handler)();
+
+    inline gsl::details::terminate_handler& get_terminate_handler() noexcept
+    {
+        static terminate_handler handler = &abort;
+        return handler;
+    }
+
+#endif
+
+    [[noreturn]] inline void terminate() noexcept
+    {
+#if defined(GSL_MSVC_USE_STL_NOEXCEPTION_WORKAROUND)
+        (*gsl::details::get_terminate_handler())();
+#else
+        std::terminate();
+#endif
+    }
+
+#if defined(GSL_TERMINATE_ON_CONTRACT_VIOLATION)
+
+    template <typename Exception>
+    [[noreturn]] void throw_exception(Exception&&)
+    {
+        gsl::details::terminate();
+    }
+
+#else
+
+    template <typename Exception>
+    [[noreturn]] void throw_exception(Exception&& exception)
+    {
+        throw exception;
+    }
+
+#endif
+
+} // namespace details
+} // namespace gsl
 
 #if defined(GSL_THROW_ON_CONTRACT_VIOLATION)
 
 #define GSL_CONTRACT_CHECK(type, cond)                                                             \
     (GSL_LIKELY(cond) ? static_cast<void>(0)                                                       \
-                      : throw gsl::fail_fast("GSL: " type " failure at " __FILE__                  \
-                                             ": " GSL_STRINGIFY(__LINE__)))
+                      : gsl::details::throw_exception(gsl::fail_fast(                              \
+                            "GSL: " type " failure at " __FILE__ ": " GSL_STRINGIFY(__LINE__))))
 
 #elif defined(GSL_TERMINATE_ON_CONTRACT_VIOLATION)
 
-#define GSL_CONTRACT_CHECK(type, cond) (GSL_LIKELY(cond) ? static_cast<void>(0) : std::terminate())
+#define GSL_CONTRACT_CHECK(type, cond)                                                             \
+    (GSL_LIKELY(cond) ? static_cast<void>(0) : gsl::details::terminate())
 
 #elif defined(GSL_UNENFORCED_ON_CONTRACT_VIOLATION)
 
diff --git a/include/gsl/gsl_util b/include/gsl/gsl_util
index 1aa8ba6..2ca171b 100644
--- a/include/gsl/gsl_util
+++ b/include/gsl/gsl_util
@@ -110,9 +110,9 @@ template <class T, class U>
 T narrow(U u)
 {
     T t = narrow_cast<T>(u);
-    if (static_cast<U>(t) != u) throw narrowing_error();
+    if (static_cast<U>(t) != u) gsl::details::throw_exception(narrowing_error());
     if (!details::is_same_signedness<T, U>::value && ((t < T{}) != (u < U{})))
-        throw narrowing_error();
+        gsl::details::throw_exception(narrowing_error());
     return t;
 }
 
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 86ce5a4..0e08d77 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -101,3 +101,64 @@ add_gsl_test(utils_tests)
 add_gsl_test(owner_tests)
 add_gsl_test(byte_tests)
 add_gsl_test(algorithm_tests)
+
+
+# No exception tests
+
+foreach(flag_var
+        CMAKE_CXX_FLAGS CMAKE_CXX_FLAGS_DEBUG CMAKE_CXX_FLAGS_RELEASE
+        CMAKE_CXX_FLAGS_MINSIZEREL CMAKE_CXX_FLAGS_RELWITHDEBINFO)
+    STRING (REGEX REPLACE "/EHsc" "" ${flag_var} "${${flag_var}}")
+endforeach(flag_var)
+
+# this interface adds compile options to how the tests are run
+# please try to keep entries ordered =)
+add_library(gsl_tests_config_noexcept INTERFACE)
+target_compile_options(gsl_tests_config_noexcept INTERFACE
+    $<$<CXX_COMPILER_ID:MSVC>:
+        /D_HAS_EXCEPTIONS=0
+        /wd4702
+        /wd4577
+        /W4
+        /WX
+    >
+    $<$<NOT:$<CXX_COMPILER_ID:MSVC>>:
+        -fno-strict-aliasing
+        -fno-exceptions
+        -Wall
+        -Wcast-align
+        -Wconversion
+        -Wctor-dtor-privacy
+        -Werror
+        -Wextra
+        -Wno-missing-braces
+        -Wnon-virtual-dtor
+        -Wold-style-cast
+        -Woverloaded-virtual
+        -Wpedantic
+        -Wshadow
+        -Wsign-conversion
+    >
+)
+
+# set definitions for tests
+target_compile_definitions(gsl_tests_config_noexcept INTERFACE
+    GSL_TERMINATE_ON_CONTRACT_VIOLATION
+)
+
+function(add_gsl_test_noexcept name)
+    add_executable(${name} ${name}.cpp)
+    target_link_libraries(${name}
+        GSL
+        gsl_tests_config_noexcept
+    )
+    add_test(
+      ${name}
+      ${name}
+    )
+    # group all tests under GSL_tests_noexcept
+    set_property(TARGET ${name} PROPERTY FOLDER "GSL_tests_noexcept")
+endfunction()
+
+add_gsl_test_noexcept(no_exception_throw_tests)
+add_gsl_test_noexcept(no_exception_ensure_tests)
diff --git a/tests/no_exception_ensure_tests.cpp b/tests/no_exception_ensure_tests.cpp
new file mode 100644
index 0000000..5da021e
--- /dev/null
+++ b/tests/no_exception_ensure_tests.cpp
@@ -0,0 +1,53 @@
+///////////////////////////////////////////////////////////////////////////////

+//

+// Copyright (c) 2015 Microsoft Corporation. All rights reserved.

+//

+// This code is licensed under the MIT License (MIT).

+//

+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE

+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,

+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN

+// THE SOFTWARE.

+//

+///////////////////////////////////////////////////////////////////////////////

+

+#include <cstdlib>      // for std::exit

+#include <gsl/span>     // for span

+

+int operator_subscript_no_throw()

+{

+    int arr[10]; 

+    gsl::span<int> sp { arr };

+    return sp[11];

+}

+

+

+void test_terminate()

+{ 

+    std::exit(0);

+}

+

+void setup_termination_handler()

+{

+#if defined(_MSC_VER)

+

+    auto& handler = gsl::details::get_terminate_handler();

+    handler = &test_terminate;

+

+#else

+

+    std::set_terminate(test_terminate);

+

+#endif

+}

+

+

+int main()

+{

+    setup_termination_handler();

+    operator_subscript_no_throw();

+    return -1;

+}

diff --git a/tests/no_exception_throw_tests.cpp b/tests/no_exception_throw_tests.cpp
new file mode 100644
index 0000000..dd4e994
--- /dev/null
+++ b/tests/no_exception_throw_tests.cpp
@@ -0,0 +1,51 @@
+///////////////////////////////////////////////////////////////////////////////

+//

+// Copyright (c) 2015 Microsoft Corporation. All rights reserved.

+//

+// This code is licensed under the MIT License (MIT).

+//

+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE

+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,

+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN

+// THE SOFTWARE.

+//

+///////////////////////////////////////////////////////////////////////////////

+

+#include <cstdlib>      // for std::exit

+#include <gsl/gsl_util> // for narrow

+

+int narrow_no_throw()

+{

+    long long bigNumber = 0x0fffffffffffffff;

+    return gsl::narrow<int>(bigNumber); 

+}

+

+void test_terminate()

+{ 

+    std::exit(0);

+}

+

+void setup_termination_handler()

+{

+#if defined(_MSC_VER)

+

+    auto& handler = gsl::details::get_terminate_handler();

+    handler = &test_terminate;

+

+#else

+

+    std::set_terminate(test_terminate);

+

+#endif

+}

+

+

+int main()

+{

+    setup_termination_handler();

+    narrow_no_throw();

+    return -1;

+}