Compilation warnings

[ginkage]

src/T67XX.cpp: In member function 'uint8_t T67XX::setSlaveAddress(uint8_t)':
src/T67XX.cpp:147:1: warning: no return statement in function returning non-void [-Wreturn-type]
 };
 ^
src/T67XX.cpp: In member function 'bool T67XX::beginCalibration()':
src/T67XX.cpp:157:63: warning: no return statement in function returning non-void [-Wreturn-type]
 bool T67XX::beginCalibration(void) { beginCalibration(false); };
                                                               ^
src/T67XX.cpp: In member function 'bool T67XX::beginCalibration(bool)':
src/T67XX.cpp:172:1: warning: no return statement in function returning non-void [-Wreturn-type]
 };
 ^
src/T67XX.cpp: In member function 'bool T67XX::endCalibration()':
src/T67XX.cpp:180:1: warning: no return statement in function returning non-void [-Wreturn-type]
 };
 ^

[curious-man]

I have got compilation error for this reason for ESP8266