For this specific case, warnings can save you: https://wandbox.org/permlink/wwbCYysH039z3YqN https://wandbox.org/permlink/wwbCYysH039z3YqN prog.cc: In funct

For this specific case, warnings can save you: https://wandbox.org/permlink/wwbCYysH039z3YqN https://wandbox.org/permlink/wwbCYysH039z3YqN prog.cc: In function 'int main()': prog.cc:8:16: error: comparison of unsigned expression < 0 is always false [-Werror=type-limits] int ru = 0 > u0 - u1; ~~^~~~~~~~~