# C_STANDARD

Added in version 3.1.

The C standard whose features are requested to build this target.

This property specifies the C standard whose features are requested to build this target. For some compilers, this results in adding a flag such as `-std=gnu11` to the compile line. For compilers that have no notion of a C standard level, such as Microsoft Visual C++ before VS 16.7, this property has no effect.

Supported values are:

`90`

  C89/C90

`99`

  C99

`11`

  C11

`17`

  Added in version 3.21.

  C17

`23`

  Added in version 3.21.

  C23

If the value requested does not result in a compile flag being added for the compiler in use, a previous standard flag will be added instead. This means that using:

    set_property(TARGET tgt PROPERTY C_STANDARD 11)

with a compiler which does not support `-std=gnu11` or an equivalent flag will not result in an error or warning, but will instead add the `-std=gnu99` or `-std=gnu90` flag if supported. This "decay" behavior may be controlled with the `C_STANDARD_REQUIRED` target property. Additionally, the `C_EXTENSIONS` target property may be used to control whether compiler-specific extensions are enabled on a per-target basis.

See the `cmake-compile-features(7)` manual for information on compile features and a list of supported compilers.

This property is initialized by the value of the `CMAKE_C_STANDARD` variable if it is set when a target is created.