cmake无法编译为C ++ 11标准 [英] cmake will not compile to C++ 11 standard

问题描述

我是C ++的新手，一直在努力进行编译/制作/链接/构建/其他操作，让我们看看是否有人可以帮助我。我进行了一些搜索，发现其他人也遇到类似的问题，但是我没有运气尝试过他们的解决方案，所以去了：

I'm new to C++ and have been struggling with compiling/making/linking/building/whatever, lets see if somebody can help me out. I did some searches and found other people with similar problems but I tried their solutions with no luck, so here goes:

使用C ++ 11功能的简单c ++程序，例如统一初始化，线程， to_string 等...生成的错误是 xxx未在作用域中声明。现在特别要使用 to_string ，并在 std 命名空间或 std :: to_string 创建错误 to_string不是STD成员。所以很明显它不是用C ++ 11编译的。

A simple c++ program that uses C++ 11 functionality such as uniform initialization, threads, to_string, etc... generates errors that "xxx" was not declared in the scope. Specifically right now I'd like to use to_string, and using it in the std namespace or specifically std::to_string creates the error "to_string" is not a member of STD. So clearly it's not compiling with C++ 11.

所以这是我的make文件：

So here's my make file:

#####################################
cmake_minimum_required (VERSION 2.8)
project (raspicam_test)
find_package(raspicam REQUIRED)
find_package(OpenCV)

IF  ( OpenCV_FOUND AND raspicam_CV_FOUND)
        MESSAGE(STATUS "COMPILING OPENCV TESTS")
        add_executable (main main.cpp)
        #target_compile_features(main PRIVATE cxx_range_for)
        set_property(TARGET main PROPERTY CXX_STANDARD 11)
        target_link_libraries (main ${raspicam_CV_LIBS})
ELSE()
        MESSAGE(FATAL_ERROR "OPENCV NOT FOUND IN YOUR SYSTEM")
ENDIF()
#####################################

当您可以看到我在树莓派上玩OpenCV。但是，如果没有C ++ 11函数，该程序就可以编译并运行。但是我想从C ++ 11添加线程和其他东西。我根据CMAKE文档添加了 set_property（TARGET main PROPERTY CXX_STANDARD_REQUIRED 11）行：

As you can see I'm playing around with OpenCV on a raspberry pi. But without the C++11 functions the program compiles and runs no issues. But I would like to add threads and other goodies from C++11. I added the line set_property(TARGET main PROPERTY CXX_STANDARD_REQUIRED 11) according to the CMAKE documentation:

https://cmake.org/cmake/help/v3.1/prop_tgt/CXX_STANDARD.html

并且生成的错误没有区别。我首先没有 _REQUIRED 做到了，然后有了它。我还尝试了 target_compile_features（），但是CMAKE返回了未知的CMAKE命令。

And it made no difference in the errors generated. I did it first without the _REQUIRED and then with it. I also tried target_compile_features() instead but CMAKE returned with "unknown CMAKE command".

其他详细信息：
-在运行debian jessie的raspberry pi 3上编译
-CXX编译器是GNU 4.9.2
-CMAKE 3.0.2

Other details: -Compiling on a raspberry pi 3 running debian jessie -CXX compiler is GNU 4.9.2 -CMAKE 3.0.2

推荐答案

在<3.1> 之前的CMake版本中，我们使用

In CMake versions earlier than 3.1, we use

 add_compile_options(-std=c++11) # CMake 2.8.12 or newer

将编译选项添加到 CMake文档中所述。

to add compile options to the compiler call as described in the CMake Docs.

这可能不像Alvaro的回答那样可移植，但是它更具可读性，而且由于您在使用RasPi，我想GCC和Clang就像目标编译器一样。

That's propably not as portable as the one in Alvaro's answer, but it's more readable and since you are on you RasPi, I guess, GCC and Clang as target compilers will do.

编辑：为了完整起见：在CMake版本 3.1和更高版本中，如果要强制使用C ++ 11，则需要执行以下操作：行：

For the sake of completeness: In CMake version 3.1 and newer, if you want to force C++11, you need the following lines:

set(CMAKE_CXX_STANDARD 11) # C++11...
set(CMAKE_CXX_STANDARD_REQUIRED ON) #...is required...
set(CMAKE_CXX_EXTENSIONS OFF) #...without compiler extensions like gnu++11

这将启用编译期间所有目标的选项。如果您想更细致地控制它，请参阅Alvaro的答案或 set_taget_properties（）的CMake文档，然后看起来像这样：

This enables the options for all targets during compilation. If you want to control this more fine-grained, see Alvaro's answer or the CMake Docs of set_taget_properties(), which then looks something like this:

set_target_properties(myTarget PROPERTIES
    CXX_STANDARD 11
    CXX_STANDARD_REQUIRED ON
    CXX_EXTENSIONS OFF
)

编辑：但是请注意，GCC 4中的C ++ 11支持并不完整，可能行为与定义的标准不同。

But beware that C++11 support in GCC 4 is not complete and there might be things that behave differently from the defined standard.

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