-std=c++11 How to activate C++ 11 in CMake?




6 Answers

The CMake command target_compile_features() is used to specify the required C++ feature cxx_range_for. CMake will then induce the C++ standard to be used.

cmake_minimum_required(VERSION 3.1.0 FATAL_ERROR)
project(foobar CXX)
add_executable(foobar main.cc)
target_compile_features(foobar PRIVATE cxx_range_for)

There is no need to use add_definitions(-std=c++11) or to modify the CMake variable CMAKE_CXX_FLAGS, because CMake will make sure the C++ compiler is invoked with the appropriate command line flags.

Maybe your C++ program uses other C++ features than cxx_range_for. The CMake global property CMAKE_CXX_KNOWN_FEATURES lists the C++ features you can choose from.

Instead of using target_compile_features() you can also specify the C++ standard explicitly by setting the CMake properties CXX_STANDARD and CXX_STANDARD_REQUIRED for your CMake target.

See also my more detailed answer.

cmake c++11 command line

When I try to run CMake generated makefile to compile my program, I get the error that

range based for loops are not supported in C++ 98 mode.

I tried adding add_definitions(-std=c++0x) to my CMakeLists.txt, but it did not help. I tried this too:

if(CMAKE_COMPILER_IS_GNUCXX)
    add_definitions(-std=gnu++0x)
endif()

When I do g++ --version, I get:

g++ (Ubuntu/Linaro 4.6.1-9ubuntu3) 4.6.1

I have also tried SET(CMAKE_CXX_FLAGS "-std=c++0x"), which also does not work.

I do not understand how I can activate C++ 11 features using CMake.




The easiest way to set the Cxx standard is:

 set_property(TARGET tgt PROPERTY CXX_STANDARD 11)

See the CMake documentation for more details.




The easiest way:

add_compile_options(-std=c++11)




What works for me is to set the following line in your CMakeLists.txt:

set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")

Setting this command activates the C++11 features for the compiler and after executing the cmake .. command, you should be able to use range based for loops in your code and compile it without any errors.




I think just these two lines are enough.

set(CMAKE_CXX_STANDARD 11)

set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")



OS X and Homebrew LLVM related:

Don't forget to call cmake_minimum_required(VERSION 3.3) and project() after it!

Or CMake will insert project() implicitly before line 1, causing trouble with Clang version detection and possibly other sorts of troubles. Here is a related issue.




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Tags

c++11   cmake