Re: Tasking differences

[Kilgallen@eisner.decus.org.nospam (Larry Kilgallen)]

In article <8kihp8$1cp$1@nnrp1.deja.com>, Robert Dewar <robert_dewar@my-deja.com> writes:
> In article <sWAj2hU9Vh4n@eisner.decus.org>,
>   Kilgallen@eisner.decus.org.nospam (Larry Kilgallen) wrote:
>> In article <8kgkdp$kjv$1@nnrp1.deja.com>, Robert Dewar
> <robert_dewar@my-deja.com> writes:
>>
>> > Certainly if the problem is that you have multiple tasks
> doing
>> > Put to the same file without synchronization, then
> absolutely
>> > anything may happen when you run the program!
>>
>> But for some given compiler/OS, it might be perfectly orderly
>> for situations like log files where the order of the records
>> is not of concern.
> 
> The problem is FAR worse than arbitrary interleaving. You are
> doing uncoordinated writes to a variable (the internal file
> variable), so the program is erroneous. Arbitrary interleaving
> is actually a very nice behavior, but a program crash due to
> inconsistent data structures is not unexpected in this situation
> (or at least should NOT be unexpected). If you want this kind
> of interleaving, you need to provide a synchronizing agent

Or ensure your tools provide it.  The DEC Ada Runtime Library is
on the VMS Listings kit.  There are calls to lock and unlock file
variables made during file operations.  Whether those calls are
perfect is certainly less tested than whether 1 + 1 = 2.