Re: Weird failure with autoconf 2.69c in gmp

[Nick Bowler]

On 2020-10-14, Ross Burton <ross@burtonini.com> wrote:
> No it's the # in the URL. Simply removing #libidn2 fixes this problem.
>
> Presumably some quoting problem which just needs more precision []?
[...]
> On Wed, 14 Oct 2020 at 09:26, Ross Burton <ross@burtonini.com> wrote:
>>
>> Similar in libidn2:
>>
>> | m4:configure.ac:16: Warning: excess arguments to builtin `m4_define'
>> ignored
>>
>>      16 AC_INIT([libidn2], [2.3.0], [help-libidn@gnu.org],,
>>      17   [https://www.gnu.org/software/libidn/#libidn2])

Yes, very similar quoting bug introduced by the same commit, but a bit
more subtle this time:

  m4_ifndef([AC_PACKAGE_URL],
          [m4_define([AC_PACKAGE_URL],
                     m4_default(m4_defn([_ac_init_URL]),
                                [m4_if(m4_index(m4_defn([_ac_init_NAME]),
                                                [GNU ]), [0],
      [[https://www.gnu.org/software/]m4_defn([AC_PACKAGE_TARNAME])[/]])]))])

If _ac_init_URL is nonempty it is insufficiently quoted in the expansion
of m4_default; since the expansion introduces a comment (because of the #)
that comment will eat some of the parentheses in this snippet and the
resulting parse is very much not right.

I probably would write this snippet something like:

  m4_define([AC_PACKAGE_URL],
    m4_ifnblank(m4_defn([_ac_init_URL]),
      [m4_defn([_ac_init_URL])], ...))

Cheers,
  Nick