Re: Bug#183730: zsh: setting SAVEHIST breaks history saving without warning

Re: Bug#183730: zsh: setting SAVEHIST breaks history saving without warning

[Clint Adams]

Maybe there should be a truncation warning.

1% SAVEHIST=899795648511
2% print $SAVEHIST
2147483647
3% SAVEHIST=899795648512
4% print $SAVEHIST
0

Re: Bug#183730: zsh: setting SAVEHIST breaks history saving without warning

[Clint Adams]

> Maybe there should be a truncation warning.
> 
> 1% SAVEHIST=899795648511
> 2% print $SAVEHIST
> 2147483647
> 3% SAVEHIST=899795648512
> 4% print $SAVEHIST

Or an error?

Re: Bug#183730: zsh: setting SAVEHIST breaks history saving without warning

[Peter Stephenson]

Clint Adams wrote:
> > Maybe there should be a truncation warning.
> > 
> > 1% SAVEHIST=899795648511
> > 2% print $SAVEHIST
> > 2147483647
> > 3% SAVEHIST=899795648512
> > 4% print $SAVEHIST
> 
> Or an error?

(Why does this `break history saving'?  Or is the subject line
inaccurate?  I'll assume the latter for now.)

I suspect there could be a lot of problems like this.  History numbering
ought to wrap gracefully, but I expect it doesn't.  Also, arithmetic is
done as a `zlong' which is probably 64 bits if the compiler supports
it, while the history size and many other parameters are only 32 bits.

Consequently there are lots of place which would need to change to make
this sort of thing consistent,
- the history code itself
- where integers from arithmetic expresssions are assigned to variables
  (though maybe it would be more consistent to use zlong for parameters
  set by the user)
- where numbers are originally parsed.

The number assigned is obviously too large to be directly useful; what
was the intention?  Always save values at the end of the history list
regardless of what was there already?

-- 
Peter Stephenson <pws@csr.com>                  Software Engineer
CSR Ltd., Science Park, Milton Road,
Cambridge, CB4 0WH, UK                          Tel: +44 (0)1223 692070


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Re: Bug#183730: zsh: setting SAVEHIST breaks history saving without warning

[Clint Adams]

> (Why does this `break history saving'?  Or is the subject line
> inaccurate?  I'll assume the latter for now.)

I think he set SAVEHIST to some enormously large value which wrapped to
0, and thus the saving of his history was "broken", without a clear
indication why.

> The number assigned is obviously too large to be directly useful; what
> was the intention?  Always save values at the end of the history list
> regardless of what was there already?

Perhaps.  Tollef, could you elaborate?

Re: Bug#183730: zsh: setting SAVEHIST breaks history saving without warning

[Peter Stephenson]

Clint Adams wrote:
> > (Why does this `break history saving'?  Or is the subject line
> > inaccurate?  I'll assume the latter for now.)
> 
> I think he set SAVEHIST to some enormously large value which wrapped to
> 0, and thus the saving of his history was "broken", without a clear
> indication why.

What could happen is the value when converted to int appeared negative
--- that would cause it to be set to zero.  More care with casts and
conversions ought to fix that.

-- 
Peter Stephenson <pws@csr.com>                  Software Engineer
CSR Ltd., Science Park, Milton Road,
Cambridge, CB4 0WH, UK                          Tel: +44 (0)1223 692070


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intended solely for the use of the individual or entity to whom they
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This footnote also confirms that this email message has been swept by
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www.mimesweeper.com
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