GSL/include/gsl/assert

///////////////////////////////////////////////////////////////////////////////
//
// 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.
//
///////////////////////////////////////////////////////////////////////////////

#ifndef GSL_CONTRACTS_H
#define GSL_CONTRACTS_H

#include <atomic>
#include <utility>

//
// 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(_KERNEL_MODE) || (defined(_HAS_EXCEPTIONS) && !_HAS_EXCEPTIONS))

#define GSL_MSVC_USE_STL_NOEXCEPTION_WORKAROUND
#include <intrin.h>
#define RANGE_CHECKS_FAILURE 0

#if defined(__clang__)
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Winvalid-noreturn"
#endif // defined(__clang__)

#else // defined(_MSC_VER) && (defined(_KERNEL_MODE) || (defined(_HAS_EXCEPTIONS) &&
      // !_HAS_EXCEPTIONS))

#include <exception>

#endif // defined(_MSC_VER) && (defined(_KERNEL_MODE) || (defined(_HAS_EXCEPTIONS) &&
       // !_HAS_EXCEPTIONS))

//
// make suppress attributes parse for some compilers
// Hopefully temporary until suppression standardization occurs
//
#if defined(__clang__)
#define GSL_SUPPRESS(x) [[gsl::suppress("x")]]
#else
#if defined(_MSC_VER) && !defined(__INTEL_COMPILER)
#define GSL_SUPPRESS(x) [[gsl::suppress(x)]]
#else
#define GSL_SUPPRESS(x)
#endif // _MSC_VER
#endif // __clang__

#define GSL_STRINGIFY_DETAIL(x) #x
#define GSL_STRINGIFY(x) GSL_STRINGIFY_DETAIL(x)

//
// GSL.assert: assertions
//

namespace gsl
{

namespace details
{
#if defined(GSL_MSVC_USE_STL_NOEXCEPTION_WORKAROUND)

    typedef void(__cdecl* terminate_handler)();

    // clang-format off
    GSL_SUPPRESS(f.6) // NO-FORMAT: attribute
    // clang-format on
    [[noreturn]] inline void __cdecl default_terminate_handler()
    {
        __fastfail(RANGE_CHECKS_FAILURE);
    }

    inline gsl::details::terminate_handler& get_terminate_handler() noexcept
    {
        static terminate_handler handler = &default_terminate_handler;
        return handler;
    }

#endif // defined(GSL_MSVC_USE_STL_NOEXCEPTION_WORKAROUND)

    [[noreturn]] inline void terminate() noexcept
    {
#if defined(GSL_MSVC_USE_STL_NOEXCEPTION_WORKAROUND)
        (*gsl::details::get_terminate_handler())();
#else
        std::terminate();
#endif // defined(GSL_MSVC_USE_STL_NOEXCEPTION_WORKAROUND)
    }

} // namespace details


class contract_group {
public:
#ifdef __cpp_noexcept_function_type
    using handler = void (*)() noexcept;
#else // VESTIGIAL, remove when no longer needed for downlevel compilers
    using handler = void (*)();
#endif

    constexpr contract_group  (handler h = nullptr)  : chandler(sanitize(h)) { }
#if __cplusplus >= 202002L
    constexpr auto set_handler(handler h) -> handler { return std::exchange(chandler, sanitize(h)); }
#else // VESTIGIAL, remove when no longer needed for downlevel compilers
    constexpr auto set_handler(handler h) -> handler { auto old = chandler; chandler = sanitize(h); return old; }
#endif
    constexpr auto get_handler()          -> handler { return chandler; }

    constexpr void expects  (bool b) { assertion(b); }
    constexpr void ensures  (bool b) { assertion(b); }
private:
    constexpr void assertion(bool b) { if (!b) chandler(); }
    constexpr auto sanitize(handler h) -> handler { return h ? h : []()noexcept{}; }
    handler chandler;
};

auto static Default = contract_group( 
#if defined GSL_TERMINATE_ON_CONTRACT_VIOLATION
                                      &gsl::details::terminate
#else // if defined GSL_UNENFORCED_ON_CONTRACT_VIOLATION
                                      // use default == null handler
#endif
                                    );

auto static Bounds  = contract_group( Default.get_handler() );
auto static Null    = contract_group( Default.get_handler() );
auto static Testing = contract_group( Default.get_handler() );

} // namespace gsl

#define Expects(cond, kind) kind.expects(cond)
#define Ensures(cond, kind) kind.ensures(cond)

#if defined(GSL_MSVC_USE_STL_NOEXCEPTION_WORKAROUND) && defined(__clang__)
#pragma clang diagnostic pop
#endif

#endif // GSL_CONTRACTS_H