Re: Bug in largefile.m4

[Paul Eggert]

[I'm sending this separately to autoconf-patches since I misspelled
 the address the first time.  The other recipients are
 address@hidden and address@hidden

> Date: Tue, 5 Dec 2000 22:22:48 +0100 (MET)
> From: Joerg Schilling <address@hidden>

> It may not be a good ides to run the largefile check first because it
> causes confdefs.h to contain the macros that activate large file support.
> If you do this you will not be able to check how/if at all to switch
> to a mixed mode application.

AC_SYS_LARGEFILE does not support mixed-mode compilation where some
bits of code in an application use 32-bit file offsets while other
bits of code use 64-bit file offsets.  The whole point of
AC_SYS_LARGEFILE is to avoid using mixed-mode, as it is a maintenance
nightmare.

If someone needs mixed mode perhaps they could contribute support for
it.  Most developers would rather use a macro that compiles code in a
single mode, though, and that is what AC_SYS_LARGEFILE is for.  Mixed
mode might be necessary for some closed-source applications, but I've
never seen a need for it in GNU applications.

> I would really do this with mkisofs. The ISO-9660 filesystem does
> not support large files at all and I need to allow the output FS image
> to ba a lage file (for a DVD). If I cannot do this, I would need
> to add checks at various places to make sure no large file is put
> on the ISO FS.

Is your point that you need mixed-mode compilation for mkisofs?  If
so, I don't understand the point.  If your mkisofs is portable, you
must add checks anyway, since off_t might be 64-bits even without
large-file compilation (e.g. Linux on the Alpha, or 64-bit Solaris
sparc).  And since you should add those checks anyway, I don't see why
mixed-mode compilation helps you.

> If you are interested, my aclocal.m4 is 28kB and is needed for
> autoconf-2.13 because of missing features and bugs....

Only 28 kB?  The latest textutils aclocal.m4 is 113 kB.  :-)

That is why the autoconf folks are working hard on the next version.