iceoryx_hoofs/cxx/attributes.hpp

Namespaces

Name
iox building block to easily create free function for logging in a library context
iox::cxx

Defines

	Name
	IOX_DISCARD_RESULT(expr) if a function has a return value which you do not want to use then you can wrap the function with that macro. Purpose is to suppress the unused compiler warning by adding an attribute to the return value
	IOX_NO_DISCARD IOX_NO_DISCARD adds the [[nodiscard]] keyword if it is available for the current compiler. If additionally the keyword [[gnu::warn_unused]] is present it will be added as well.
	IOX_FALLTHROUGH IOX_FALLTHROUGH adds the [[fallthrough]] keyword when it is available for the current compiler.
	IOX_MAYBE_UNUSED IOX_MAYBE_UNUSED adds the [[gnu::unused]] or [[maybe_unused]] attribute when it is available for the current compiler.

Macro Documentation

define IOX_DISCARD_RESULT

#define IOX_DISCARD_RESULT(
    expr
)
static_cast<void>(expr)

if a function has a return value which you do not want to use then you can wrap the function with that macro. Purpose is to suppress the unused compiler warning by adding an attribute to the return value

Parameters:

• expr name of the function where the return value is not used.

uint32_t foo();
IOX_DISCARD_RESULT(foo()); // suppress compiler warning for unused return value

define IOX_NO_DISCARD

#define IOX_NO_DISCARD 

IOX_NO_DISCARD adds the [[nodiscard]] keyword if it is available for the current compiler. If additionally the keyword [[gnu::warn_unused]] is present it will be added as well.

Note: [[nodiscard]], [[gnu::warn_unused]] supported since clang 3.9 (https://clang.llvm.org/cxx_status.html) activate keywords for gcc>=5 or clang>=4

define IOX_FALLTHROUGH

#define IOX_FALLTHROUGH 

IOX_FALLTHROUGH adds the [[fallthrough]] keyword when it is available for the current compiler.

Note: [[fallthrough]] supported since clang 3.9 (https://clang.llvm.org/cxx_status.html) activate keywords for gcc>=7 or clang>=4

define IOX_MAYBE_UNUSED

#define IOX_MAYBE_UNUSED 

IOX_MAYBE_UNUSED adds the [[gnu::unused]] or [[maybe_unused]] attribute when it is available for the current compiler.

Note: activate attribute for gcc or clang

Source code

// Copyright (c) 2021 by Apex.AI Inc. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
// SPDX-License-Identifier: Apache-2.0
#ifndef IOX_HOOFS_CXX_ATTRIBUTES_HPP
#define IOX_HOOFS_CXX_ATTRIBUTES_HPP

namespace iox
{
namespace cxx
{
// NOLINTNEXTLINE
#define IOX_DISCARD_RESULT(expr) static_cast<void>(expr)

//    [[nodiscard]], [[gnu::warn_unused]] supported since gcc 4.8 (https://gcc.gnu.org/projects/cxx-status.html)
#if defined(_WIN32)
// On WIN32 we are using C++17 which makes the keyword [[nodiscard]] available
// NOLINTNEXTLINE
#define IOX_NO_DISCARD [[nodiscard]]
#elif defined(__APPLE__) && defined(__clang__)
// On APPLE we are using C++17 which makes the keyword [[nodiscard]] available
// NOLINTNEXTLINE
#define IOX_NO_DISCARD [[nodiscard, gnu::warn_unused]]
#elif (defined(__clang__) && __clang_major__ >= 4)
// NOLINTNEXTLINE
#define IOX_NO_DISCARD [[gnu::warn_unused]]
#elif (defined(__GNUC__) && __GNUC__ >= 5)
// NOLINTNEXTLINE
#define IOX_NO_DISCARD [[nodiscard, gnu::warn_unused]]
#else
// on an unknown platform we use for now nothing since we do not know what is supported there
#define IOX_NO_DISCARD
#endif

//    [[fallthrough]] supported since gcc 7 (https://gcc.gnu.org/projects/cxx-status.html)
#if defined(_WIN32)
// On WIN32 we are using C++17 which makes the keyword [[fallthrough]] available
// NOLINTNEXTLINE
#define IOX_FALLTHROUGH [[fallthrough]]
#elif defined(__APPLE__) && defined(__clang__)
// On APPLE we are using C++17 which makes the keyword [[fallthrough]] available
// NOLINTNEXTLINE
#define IOX_FALLTHROUGH [[fallthrough]]
#elif (defined(__GNUC__) && __GNUC__ >= 7) && !defined(__clang__)
// clang prints a warning therefore we exclude it here
// NOLINTNEXTLINE
#define IOX_FALLTHROUGH [[fallthrough]]
#else
// on an unknown platform we use for now nothing since we do not know what is supported there
#define IOX_FALLTHROUGH
#endif

#if defined(__GNUC__) || defined(__clang__)
// NOLINTNEXTLINE
#define IOX_MAYBE_UNUSED [[gnu::unused]]
#elif defined(_WIN32)
// On WIN32 we are using C++17 which makes the attribute [[maybe_unused]] available
// NOLINTNEXTLINE
#define IOX_MAYBE_UNUSED [[maybe_unused]]
// on an unknown platform we use for now nothing since we do not know what is supported there
#else
#define IOX_MAYBE_UNUSED
#endif


} // namespace cxx
} // namespace iox

#endif

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Updated on 2 April 2022 at 16:37:47 CEST