[tex-live] Re: [tex-implementors] Re: bug in etex

[Philip TAYLOR]

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.