[M3devel] Unnecessary(?) range confusion in ThreadPosix.m3

[Mika Nystrom]

Dear Modula-3 people,

I had a crash in my program from a range error that I believe
shouldn't have happened the way it did, although it's not in my
code, so I'm not sure if there's a reason for the way it's done (matching
a C declaration somewhere, maybe??).

Here it is, from ThreadPosix.m3:

PROCEDURE IOWait(fd: INTEGER; read: BOOLEAN;
                  timeoutInterval: LONGREAL := -1.0D0): WaitResult =
  <*FATAL Alerted*>
  BEGIN
    self.alertable := FALSE;
    RETURN XIOWait(fd, read, timeoutInterval);
  END IOWait;

PROCEDURE IOAlertWait(fd: INTEGER; read: BOOLEAN;
                  timeoutInterval: LONGREAL := -1.0D0): WaitResult
                  RAISES {Alerted} =
  BEGIN
    self.alertable := TRUE;
    RETURN XIOWait(fd, read, timeoutInterval);
  END IOAlertWait;

PROCEDURE XIOWait (fd: CARDINAL; read: BOOLEAN; interval: LONGREAL): WaitResult
    RAISES {Alerted} =
  VAR res: INTEGER;
      fdindex := fd DIV FDSetSize;
      fdset := FDSet{fd MOD FDSetSize};
... rest omitted ...

Note that IOWait calls XIOWait.  IOWait is declared as taking an
INTEGER, but XIOWait takes a CARDINAL.

So I really should use a CARDINAL in passing to IOWait, but since
IOWait is the interface function it's not clear that I should do
that (until my program crashes after passing -1 from some carelessly
wrapped C code).  I don't like the fact that I get a range error
*inside* the library when it appears unnecessary---it should have
happened in my code, as I make the call.

Suggested improvement: declare all the FDs in SchedulerPosix.i3
(the interface that exports these routines) to be CARDINAL instead
of INTEGER.

     Mika