../src/gaio buongustaio.cpp: In function ‘int main()’:
../src/gaio buongustaio.cpp:30: error: ‘gadget’ was not declared in this scope
../src/gaio buongustaio.cpp:15: warning: unused variable ‘a’
../src/gaio buongustaio.cpp:15: warning: unused variable ‘b’
../src/gaio buongustaio.cpp:15: warning: unused variable ‘z’
../src/gaio buongustaio.cpp: In function ‘int Fgadget(int&)’:
../src/gaio buongustaio.cpp:67: warning: no return statement in function returning non-void
make: *** [src/gaio buongustaio.o] Errore 1

ecco che dice il debug
grazie