Re: etex and pdftex have diverging memory constraints?

Am 27.08.25 um 15:15 schrieb jfbu via tex-live:
> 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 cannot see it with an up-to-date TL2025 (macOS):

voss>mist:$ pdfetex  xyz.tex
This is pdfTeX, Version 3.141592653-2.6-1.40.28 (TeX Live 2025) 
(preloaded format=pdfetex)
  restricted \write18 enabled.
entering extended mode
(./xyz.tex 
(/usr/local/texlive/2025/texmf-dist/tex/generic/xint/xintkernel.sty)
  [1{/usr/local/texlive/2025/texmf-var/fonts/map/pdftex/updmap/pdftex.map}] 
)</u
sr/local/texlive/2025/texmf-dist/fonts/type1/public/amsfonts/cm/cmr10.pfb>
Output written on xyz.pdf (1 page, 9876 bytes).
Transcript written on xyz.log.

Herbert