Re: if optimization and eating trailing whitespace with dnl

[Eric Blake]

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According to Mike Frysinger on 12/26/2009 10:58 AM:
> the lcd4linux package uses a common construct like so:
> 
> AC_INIT
> if :; then
>         AC_MSG_RESULT([no])
>         AC_MSG_ERROR([blah blah blah
> blah blah
> ])dnl
> fi
> AC_OUTPUT

The dnl is spurious if the package wants to be portable to a range of
autoconf versions.  I don't see how this particular snippet could have
ever worked - even back in 2.63, prior to AC_MSG_ERROR being rewritten to
call a shell function instead of always being a grouping command, it was
never valid shell to use

if :; then
AC_MSG_ERROR(...)dnl
fi

because that would expand to:

if :; then
{ ... ;}fi

Are you instead complaining about an interaction between AS_IF and
AC_MSG_ERROR?  At any rate, I don't think anything in autoconf needs to
change; rather, this package should fix their own bug by doing what you
already mentioned:

> if the dnl is dropped, or a newline is added before the fi, then the 
> generated 
> script works fine.

- --
Don't work too hard, make some time for fun as well!

Eric Blake             address@hidden
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