Re: etex and pdftex have diverging memory constraints?

Sorry Herbert.

I forgot to say I am on a 64bit system.

I have confirmed that the limits (which are close to one another with etex slightly highter than pdftex) are about half the value of main_memory parameter in texmf.cnf.

This parameter is referred to in a comment there as "words of inimemory available; " 

On my system its value is 5000000.

Perhaps you have a higher setting or are on a 32bit machine and then the limit is at about main_memory (I can't check).

Kind regards

Jean-François


> Le 27 août 2025 à 15:42, Herbert Voss <[email protected]> a écrit :
> 
> 
> 
> 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