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Re: [PATCH] warnings: fix compilation with old autoconf
From: |
Bruno Haible |
Subject: |
Re: [PATCH] warnings: fix compilation with old autoconf |
Date: |
Sun, 27 Aug 2017 19:50:01 +0200 |
User-agent: |
KMail/5.1.3 (Linux/4.4.0-92-generic; KDE/5.18.0; x86_64; ; ) |
Hi Eric,
> > Is m4_defun sufficient for AC_REQUIRE to work? The comments state that it is
> > essential that these macros can be AC_REQUIREd. This is needed for
> > gl_WARN_ADD (warnings.m4 line 94).
>
> Yes. Implementation-wise, autoconf has:
>
> m4_copy([m4_defun], [AC_DEFUN])
>
> that is, AC_DEFUN is defined as a copy of the body of m4_defun,
> expanding to the same text. Both AC_REQUIRE and m4_require are equally
> happy to pull in a macro, regardless of whether it defined via AC_DEFUN
> or m4_defun, making them interchangeable for what output is produced.
>
> Therefore, the difference between the two macros is based solely on the
> fact that tracing depends on which macro name is invoked.
Well, then the Autoconf documentation at
https://www.gnu.org/savannah-checkouts/gnu/autoconf/manual/autoconf-2.69/html_node/Macro-Definitions.html
is wrong. It states that the major difference between AC_DEFUN and m4_defun
is "some code that is used to constrain the order in which macros are
called, while avoiding redundant output (-> AC_REQUIRE)".
Care to update the documentation?
Bruno