检查是否使用CMAKE在编译器中启用了c ++ 11功能 [英] check if a c++11 feature is enabled in compiler with CMAKE

问题描述

我正在与CMake合作开发一个项目。我的代码包含 constexpr 方法，在Visual Studio 2015中允许使用，但在Visual Studio 2013中不允许。

I'm developing a project with CMake. My code contains constexpr methods, that are allowed in Visual Studio 2015, but not in Visual Studio 2013.

如何是否可以检查 CMakeLists.txt 是否受指定编译器支持？我已经在CMake文档中看到 CMAKE_CXX_KNOWN_FEATURES ，但我不知道如何使用它。

How can I check in the CMakeLists.txt if the feature is supported by the specified compiler? I've seen in CMake documentation CMAKE_CXX_KNOWN_FEATURES, but I didn't understand how to use it.

推荐答案

您可以使用 target_compile_features 要求具有C ++ 11（/ 14/17）功能：

You can use target_compile_features to require a C++11(/14/17) feature:

target_compile_features(target PRIVATE|PUBLIC|INTERFACE feature1 [feature2 ...])

具有 feature1 是 CMAKE_CXX_KNOWN_FEATURES 。例如，如果要在公共API中使用 constexpr ，则可以使用：

With feature1 being a feature listed in CMAKE_CXX_KNOWN_FEATURES. For example, if you want to use constexpr in your public API, you can use:

add_library(foo ...)
target_compile_features(foo PUBLIC cxx_constexpr)

---

您还应该查看 WriteCompilerDetectionHeader 模块，该模块允许将功能检测为选项，并在编译器不支持某些功能的情况下向后兼容实现：

---

You should also take a look at the WriteCompilerDetectionHeader module which allows to detect features as options, and provides a backward compatibility implementation for some features if the compiler does not support them:

write_compiler_detection_header(
    FILE foo_compiler_detection.h
    PREFIX FOO
    COMPILERS GNU MSVC
    FEATURES cxx_constexpr cxx_nullptr
)

此处是文件 foo_compiler_detection.h constexpr 可用，将使用定义的 FOO_COMPILER_CXX_CONSTEXPR 生成$ c>：

Here a file foo_compiler_detection.h will be generated with FOO_COMPILER_CXX_CONSTEXPR defined if the keyword constexpr is available:

#include "foo_compiler_detection.h"

#if FOO_COMPILER_CXX_CONSTEXPR

// implementation with constexpr available
constexpr int bar = 0;

#else

// implementation with constexpr not available
const int bar = 0;

#endif

此外， FOO_CONSTEXPR 并将其扩展为 constexpr 。否则将为空。

Moreover, FOO_CONSTEXPR will be defined and will expand to constexpr if the feature exists for the current compiler. It will be empty otherwise.

FOO_NULLPTR 将被定义并扩展为 nullptr （如果当前编译器存在该功能）。否则它将扩展到兼容性实现（例如 NULL ）。

FOO_NULLPTR will be defined and will expand to nullptr if the feature exists for the current compiler. It will expand to a compatibility implementation otherwise (e.g. NULL).

#include "foo_compiler_detection.h"

FOO_CONSTEXPR int bar = 0;

void baz(int* p = FOO_NULLPTR);

请参见 CMake文档。

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