如果无法满足CMAKE_CXX_STANDARD，如何在CMake中干净地错误？

Question

Cmake提供 CMAKE_CXX_STANDARD 用于指定所需的C ++标准。

set（cmake_cxx_standard 17）

但是，如果您的编译器旧了...说GCC4 ...它仍然会尝试编译来源，并且由于缺少丢失的奇异错误消息，它当然会失败编译器功能。

有没有干净的方法使CMAKE检测到这种缺失的支持并以更明显的方式失败？

Answer 1

使用target_compile_features进行更多控制

，如 kamilcuk 10149169“>他们的答案，您可以检查CXX_STD_17。

此外，您可以在目标上设置需求：

target_compile_features(my_example_library PUBLIC cxx_std_17)

源

https://cmake.org/cmake/help/help/latest/manual/cmake-compile-features.7.html#requiring-language-standards只有一些目标需要某些标准。同样的语法也可以仅需仅需要特定功能，在。

Simpler option for CMAKE_CXX_STANDARD, set CXX_STANDARD_REQUIRED

However, if you're using

# will affect any library/target defined after this
set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED TRUE)
# also recommended, uses -std=c++17 instead of -std=gnu++17
# if you code is compatible with non-GCC compilers too
# set(CMAKE_CXX_EXTENSIONS OFF)

您会收到一个错误，看起来像：

CMake Error in CMakeLists.txt:
  Target "my_example_library" requires the language dialect "C17" (with
  compiler extensions).  But the current compiler "GNU" does not support
  this, or CMake does not know the flags to enable it.

Answer 2

From https://cmake.org/cmake/help/latest/variable/CMAKE_CXX_STANDARD .html ：

请参阅CMAKE-COMPILE-FEATURES（7）手册，以获取有关编译功能和支持编译器列表的信息。

来自 https://cmake.org/cmake/help/help/latest/manual/cmake-compile-features.7.html#manual：Cmake-compile-features（7）：

cmake_c_known_features，cmake_cuda_known_features和cmake_cxx_nown_features全局属性包含CMake已知的所有功能，无论编译器对该功能的支持如何。 cmake_c_compile_features，cmake_cuda_compile_features和cmake_cxx_compile_features变量包含所有功能Cmake知道，无论是使用它们的语言标准或编译标志所需的语言标准，

来自 https://cmake.org/cmake/help/help/latest/prop_gbl/cmake_cxx_nown_nown_nown_features.html#prop_gbl：cmake_cxx_features

cxx_std_17

Compiler mode is at least C++ 17.

noreferrer

if ("cxx_std_17" IN_LIST CMAKE_CXX_COMPILE_FEATURES)