How to manage C++ standard [EXPERIMENTAL]

Warning

This is an experimental feature subject to breaking changes in future releases. Previously, it was implemented as a first level setting cppstd, we encourage you to adopt the new subsetting and update your recipes if they were including the deprecated one in its settings attribute.

The setting representing the C++ standard is compiler.cppstd. The detected default profile doesn’t set any value for the compiler.cppstd setting,

The consumer can specify it in a profile or with the -s parameter:

conan install . -s compiler.cppstd=gnu14

As it is a subsetting, it can have different values for each compiler (also, take into account that depending on the version of the compiler the standard could have only partial support and may change the ABI).

Valid values for compiler=Visual Studio:

VALUE

DESCRIPTION

14

C++ 14

17

C++ 17

20

C++ 20 (Still C++20 Working Draft)

Valid values for other compilers:

VALUE

DESCRIPTION

98

C++ 98

gnu98

C++ 98 with GNU extensions

11

C++ 11

gnu11

C++ 11 with GNU extensions

14

C++ 14

gnu14

C++ 14 with GNU extensions

17

C++ 17

gnu17

C++ 17 with GNU extensions

20

C++ 20 (Partial support)

gnu20

C++ 20 with GNU extensions (Partial support)

Build helpers

The value of compiler.cppstd provided by the consumer is used by the build helpers:

  • The CMake build helper will set the CONAN_CMAKE_CXX_STANDARD and CONAN_CMAKE_CXX_EXTENSIONS definitions that will be converted to the corresponding CMake variables to activate the standard automatically with the conan_basic_setup() macro.

  • The AutotoolsBuildEnvironment build helper will adjust the needed flag to CXXFLAGS automatically.

  • The MSBuild/VisualStudioBuildEnvironment build helper will adjust the needed flag to CL env var automatically.

Package compatibility

By default Conan will detect the default standard of your compiler to not generate different binary packages. For example, you already built some gcc 6.1 packages, where the default C++ standard is gnu14. If you introduce the compiler.cppstd setting in your profile with the gnu14 value, Conan won’t generate new packages, because it was already the default of your compiler.

Note

Check the package_id() reference to know more.

Note

Conan 1.x will also generate the same packages as the ones generated with the deprecated setting cppstd for the default value of the standard.