ios - Error :Unknown type name BOOL for c function in Xcode -

i building static library has c functions (both .h , .m file) return type bool, after adding existing project getting unknown type name 'bool'. tried importing stdbool.h still getting same error.so can tell me right way add c functions in xcode project.the method definition looks like

bool isdeviceworkingfine(); 

in stdbool.h, definition provided bool macro gets expanded _bool. bool you're using not standard c.

if want use standard definition provided stdbool.h, may want change bool bool.

otherwise, need use other specific header file, provides definition of bool implementation.^note

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note: as mentioned in comments mr blagovest buyukliev, may need <foundation/foundation.h>.