How to manage C++ standard
Caution
We are actively working to finalize the Conan 2.0 Release. Some of the information on this page references deprecated features which will not be carried forward with the new release. It’s important to check the Migration Guidelines to ensure you are using the most up to date features.
Tip
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
andCONAN_CMAKE_CXX_EXTENSIONS
definitions that will be converted to the corresponding CMake variables to activate the standard automatically with theconan_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.
Required version
When the package to be built requires a minimal C++ standard support (e.g. 17), it can be done by
comparing the cppstd
. For such condition, there is the helper check_min_cppstd.