[tex-live] Re: [tex-implementors] Re: bug in etex
Philip TAYLOR
P.Taylor at Rhul.Ac.Uk
Wed Jul 14 14:11:26 CEST 2004
Olaf Weber wrote:
[snip]
> What is null in etex in the Pascal version? In web2c it is defined as
> min_halfword, which is a large negative number (-@"FFFFFFF). However,
> in the original tex.web, min_halfword equals 0. So the reason the
> Pascal version doesn't trap may be that an invalid (null) cur_ptr,
> is still a valid array index, in contrast to web2c.
In TeX.web, NULL is @D'd to MIN_HALFWORD, which is itself @D'd to 0.
When you say "In web2c it is defined as min_halfword", I don't think
this is "web2c"-specific at all : it appears to derive directly from
Knuth's canonical Pascal code. A global search over all of the
AXP/VMS and ETEX directories does not reveal change to tbe /status
quo/ : both (VMS) TeX.ch and (VMS) eTeX.ch simply repeat that declaration :
ALPHA9::Chaa006 : search [...]*.* "@d min_halfword"
******************************
CHAA:[006.E-TEX.KNUTH]TEX.WEB;1
@d min_halfword==0 {smallest allowable value in a |halfword|}
******************************
CHAA:[006.E-TEX.VMS]ETEX_VMS.CH;5
@d min_halfword==0 {smallest allowable value in a |halfword|}
@d min_halfword==0 {smallest allowable value in a |halfword|}
******************************
CHAA:[006.E-TEX.VMS]TEX_VMS.CH;1
@d min_halfword==0 {smallest allowable value in a |halfword|}
@d min_halfword==0 {smallest allowable value in a |halfword|}
ALPHA9::Chaa006 :
** Phil.
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