Re: etex and pdftex have diverging memory constraints?

Hi

You've found a nice puzzle. Any preloaded format files uses space in the
main memory. I suspect that etex and pdftex do not occupy the same amount
of main memory. And in fact that pdftex tex occupies more.

>From my phone.

Jonathan

On Wed, 27 Aug 2025, 14:15 jfbu via tex-live, <[email protected]> wrote:

> Hi,
>
> Sorry if this is very basic, but I always thought the sole difference
> between etex and pdftex is that the former works to produce a dvi and the
> latter a pdf.
>
> So, I was surprised to discover (or perhaps I observed that years ago and
> forgot) that pdftex has slightly more constrained memory constraints on
> macro expansion.
>
> Here is a test file testxintLength.tex
>
> ----
> \input xintkernel.sty
> \edef\x{\romannumeral\xintreplicate{%
> 2492679%
> }{F}}
> \expandafter\xintLength\expandafter{\x}
> \bye
> ----
>
> (the code creates a macro \x expanding to 2492679 F's then attempts to
> measure how many F's there are).
>
> Compilation with etex succeeds  (even with 2492694 in place of 2492679).
>
> $ etex testxintLength.tex
> This is pdfTeX, Version 3.141592653-2.6-1.40.28 (TeX Live 2025) (preloaded
> format=etex)
>  restricted \write18 enabled.
> entering extended mode
> (./testxintLength.tex (./xintkernel.sty) [1] )
> Output written on testxintLength.dvi (1 page, 216 bytes).
> Transcript written on testxintLength.log.
>
> But compilation with pdftex fails.
>
> $ pdftex testxintLength
> This is pdfTeX, Version 3.141592653-2.6-1.40.28 (TeX Live 2025) (preloaded
> format=pdftex)
>  restricted \write18 enabled.
> entering extended mode
> (./testxintLength.tex (./xintkernel.sty)
> ! TeX capacity exceeded, sorry [main memory size=5000000].
> <inserted text> 2492679
>                         \xintlength ...xint_c_i \xint_c_ \xint_bye \relax
>                                                    l.5
> \expandafter\xintLength\expandafter{\x}
>                                             !  ==> Fatal error occurred,
> no output PDF file produced!
> Transcript written on testxintLength.log.
>
> I am a bit surprised because I can not connect the constraints on TeX
> macro expansion with the output format DVI or PDF.  Needless to say I am
> completely ignorant of the innards.
>
> If replying please CC as I am not on the list.
>
> Kind regards
>
> Jean-François
>
>
>