# C_EXTENSIONS

Added in version 3.1.

Boolean specifying whether compiler specific extensions are requested.

This property specifies whether compiler specific extensions should be used. For some compilers, this results in adding a flag such as `-std=gnu11` instead of `-std=c11` to the compile line. This property is `ON` by default. The basic C standard level is controlled by the `C_STANDARD` target property.

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_EXTENSIONS` variable if set when a target is created and otherwise by the value of `CMAKE_C_EXTENSIONS_DEFAULT` (see `CMP0128`).