All diagnostic messages, including errors and warnings, can be suppressed with the --quiet option. To report errors and warnings but not other assembly status information, pass the --no-stats option. The --checksum option prints an MD5 hash of the code generated.
Options exist specifically for controlling error and warning reporting. To suppress only warnings but not errors, use the --no-warn option. To output error and warning messages to a file (without using the operating system's built-in facilities for this), you can also set the -e/--error option.
6502.net.exe source.asm -o program.prg --error=errors.txt
When an error or warning is reported to the standard output, typically the source where the error occurred is highlighted.
-$ dotnet 6502.net.dll x86code.s
x86code.s(1:12): error: Unexpected: 'eax'
mov eax,ebx
^--
Use --no-highlighting to disable this feature.
There are several options specific to warning messages. To enable all warning types, set the option --Wall, while to treat all warnings as errors, pass --werror. See the reference on options for full information on all warning options available.
The developer can make assertions in their code, optionally adding a custom message if the assertion fails
.assert * < $100 // make sure we are in zero page
.assert * < $100, "Zero Page Boundary Crossed!" // add a helpful message
In a similar vein, the .errorif directive will raise an error but with the condition being met and a custom error being required.
.errorif * >= $0100, "Zero Page Boundary Crossed!"
This can be turned into warning using .warnif.
.warnif * >= $0100, "Caution: Zero Page Boundary Crossed!"
Errors and warnings can be raised unconditionally.
.error "This does not work!"
.warn "We need to refactor this!"
To print merely informational messages, use the .echo directive.
.echo $"Program Counter is ${*}"
.echo will only print the message on first pass but if the message is desired to printed each pass set the option --echo-each-pass is set.