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

[Tony Hosking]

Sounds fair to me.

On 25 Oct 2008, at 04:16, Mika Nystrom wrote:

>
> 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