### 2.16 Control Warnings: `-W`, `--warn`, `--no-warn`, `--fatal-warnings`

`as` should never give a warning or error message when assembling compiler output. But programs written by people often cause `as` to give a warning that a particular assumption was made. All such warnings are directed to the standard error file.

If you use the `-W` and `--no-warn` options, no warnings are issued. This only affects the warning messages: it does not change any particular of how `as` assembles your file. Errors, which stop the assembly, are still reported.

If you use the `--fatal-warnings` option, `as` considers files that generate warnings to be in error.

You can switch these options off again by specifying `--warn`, which causes warnings to be output as usual.