Critical Mass Modula-3: m3tk-misc/src/Err.i3

m3tk-misc/src/Err.i3

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INTERFACE Err;

This interface provides a standard mechanism for simple error reporting. The error messages are written to an error stream. This error stream is a vague concept and may be implemented different ways on different systems (some window systems might have a standard error window for example). The implementation is not important providing the programmer can rely on the fact that any messages written using Err get through to the user if it is at all possible.

Error messages are classified into five severities and a continuation:

Continue a continuation of the previous message.

Comment not an error at all; just a message (e.g. program identification, copyright notice, etc.).

Warning the program has performed in a manner, or detected something, which may cause surprise to its user, but has otherwise executed correctly (e.g. a message from a compiler flagging an unused variable).

Error the program has detected a definite error and may have had to take drastic recovery action in order to proceed (e.g. a gross syntax error detected by a compiler, leading to no code being generated).

Fatal a fatal but foreseen error which brings the program to a dead stop (e.g. failing to find a vital file or running out of workspace).

Disaster a fatal but foreseen error which brings the program to a dead halt and for which the most appropriate action is to enter the debugger, generate a postmortem dump, etc. (e.g. the program detects an internal inconsistency in its data structures or fails an assertion test).

After an error of severity Fatal the program is terminated by executing RTShutdown.Exit; after an error of severity Disaster, the program terminates by raising an uncatchable exception. This causes a postmortem dump, entry to the debugger, or other system-specific debugging action.

Messages are constructed by taking the user supplied message and prepending the program name and the severity of the error. The program name is omitted for continuations and the severity is omitted for continuations and comments. The user can specify whether a newline should be appended to the message.

The program name can be set explicitly, but a default value is otherwise used, acquired by calling Params.Get(0).

TYPE
  Severity = {Continue, Comment, Warning, Error, Fatal, Disaster};

PROCEDURE Print(msg: TEXT; severity: Severity := Severity.Fatal;
                newline: BOOLEAN := TRUE);

Constructs and prints an error message. severity is explained above. msg is the user supplied error message. newline indicates whether a newline should be appended before printing.


PROCEDURE SetProgramName(n: TEXT): TEXT;

Sets the program name used in error messages to n. The previous value is returned as result.


END Err.