On 29/07/2023 08:37, LARONDE Thierry wrote:
> On Sat, Jul 29, 2023 at 08:07:54AM +0100, Joseph Wright wrote:
>> On 29/07/2023 06:46, LARONDE Thierry wrote:
>>> On Fri, Jul 28, 2023 at 08:31:53PM +0100, David Carlisle wrote:
>>>>
>>>> % If this option is set to true, `tex a.b' will look first for a.b.tex
>>>> % (within each path element), and then for a.b, i.e., we try standard
>>>> % extensions first.  If this is false, we first look for a.b and then
>>>> % a.b.tex, i.e., we try the name as-is first.
>>>> %
>>>> % Both names are always tried; the difference is the order in which they
>>>> % are tried.  The setting applies to all searches, not just .tex.
>>>> %
>>>> % This setting only affects names being looked up which *already* have
>>>> % an extension.  A name without an extension (e.g., `tex story') will
>>>> % always have an extension added first.
>>>> %
>>>> % The default is true, because we already avoid adding the standard
>>>> % extension(s) in the usual cases.  E.g., babel.sty will only look for
>>>> % babel.sty, not babel.sty.tex, regardless of this setting.
>>>> try_std_extension_first = t
>>>
>>> I suppose that this behavior is in LaTeX code, not an engine?
>>
>> That's from texmf.cnf, so affects most engines. (LuaMetaTeX like unaffected:
>> I'd have to check.)
> 
> This does mean that this behavior is not in the engine but in the glue
> code (the opening routines implemented in web2c/kpathsea)? So its
> setting is done at configuration level in the distribution, and LaTeX
> has no way to switch things from its macro files?

Yes, as file handling is of course not part of the portable TeX code.

> Because in order to do
> so, another primitive should be added?

Why? The current behaviour is well defined.

> Does LaTeX rely on a behavior that is not in the engines but only in the
> web2c distribution?

No, and we *don't here*: adding .tex is a feature of TeX not web2c.

Joseph