Date: Wed, 21 Mar 2001 21:42:22 +0200
From: "Eli Zaretskii" <eliz AT is DOT elta DOT co DOT il>
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To: Martin Str|mberg <ams AT father DOT ludd DOT luth DOT se>
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In-reply-to: <99asp4$9a2$1@news.luth.se> (message from Martin Str|mberg on
	Wed, 21 Mar 2001 18:43:48 +0000 (UTC))
Subject: Re: Freedos, INT 0x21, AX=0x71a0 and emacs
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> From: Martin Str|mberg <ams AT father DOT ludd DOT luth DOT se>
> Newsgroups: comp.os.msdos.djgpp
> Date: Wed, 21 Mar 2001 18:43:48 +0000 (UTC)
> 
> FreeDOS does not support LFN so I find that every program generates
> one INT 0x21, AX=0x71a0 at start-up. This is expected.
> 
> However when I start emacs there are many (more than 25) calls to this
> function. That seems like a waste. Is emacs designed to behave like
> this or is there a bug lurking somewhere?

It's not a bug.  The library startup code issues one call to 71A0h, to
find out whether LFN is supported, and then caches the result to be
used by all library functions.

But Emacs also needs this information in its application code, to know
whether a certain feature which requires long file names can or cannot
be used.  There's a special function, msdos-long-file-names, which
returns nil or t depending on whether LFN is or isn't supported.  What
you see is the 71A0h calls that function emits.

In other words, Emacs is simply a program that checks whether LFN is
supported in many places in its application code, while other programs
you tested do not do that.