Why should I always enable compiler warnings?

Question

I often hear that when compiling C and C++ programs I should \"always enable compiler warnings\". Why is this necessary? How do I do that?

Sometimes I also hear tha

Answer 1

Some warning may mean possible semantic error in code or possible UB. E.g. ; after if(), unused variable, global variable masked by local, or comparison of signed and unsigned. Many warnings are related to static code analyzer in compiler or to breaches of ISO standard detectable at compile time, which "require diagnostics". While those occurrences may be legal in one particular case, they would be result of design issues most of time.

Some compilers, e.g. gcc, have a command line option to activate "warnings as errors" mode, it's a nice , if cruel, tool to educate novice coders.