Re: autoconf-2.69c released [beta]

[Zack Weinberg]

On Sat, Sep 26, 2020 at 8:15 AM Gavin Smith <gavinsmith0123@gmail.com> wrote:
> On Fri, Sep 25, 2020 at 9:07 PM Gavin Smith <gavinsmith0123@gmail.com> wrote:
> >
> > > * Warnings about obsolete constructs are now on by default.
> > >   They can be turned off with '-Wno-obsolete'.
> > >
> >
> > I have tried building the git development version of Texinfo with
> > the new autoconf, but am deluged with warnings.  I get the following
> > warnings from autoconf:
> >
> > configure.ac:87: warning: The macro `AC_GNU_SOURCE' is obsolete.
> > configure.ac:87: You should run autoupdate.
> > ./lib/autoconf/specific.m4:312: AC_GNU_SOURCE is expanded from...
> > gnulib/m4/gnulib-comp.m4:34: gl_EARLY is expanded from...
> > configure.ac:87: the top level
>
> I found it hard to track down where the AC_GNU_SOURCE use was coming
> from, and the path "lib/autoconf/specific.m4" is incorrect for the
> file "specific.m4".

Yes, unfortunately, the m4 backtrace emitted by configure warnings
doesn't handle AC_REQUIREd macros correctly.  Fixing this is probably
not feasible for 2.70.

> By searching for the text AC_GNU_SOURCE in all
> project files as well as installed autoconf files, as well as looking
> at the log files under autom4te.cache, I suspect it is coming from the
> "extensions.m4" file from Gnulib. (I don't know why that file isn't
> named in the error messages, though.) This has the following
> definition:
>
> # gl_USE_SYSTEM_EXTENSIONS
> # ------------------------
> # Enable extensions on systems that normally disable them,
> # typically due to standards-conformance issues.
> AC_DEFUN_ONCE([gl_USE_SYSTEM_EXTENSIONS],
> [
>   dnl Require this macro before AC_USE_SYSTEM_EXTENSIONS.
>   dnl gnulib does not need it. But if it gets required by third-party macros
>   dnl after AC_USE_SYSTEM_EXTENSIONS is required, autoconf 2.62..2.63 emit a
>   dnl warning: "AC_COMPILE_IFELSE was called before AC_USE_SYSTEM_EXTENSIONS".
>   dnl Note: We can do this only for one of the macros AC_AIX, AC_GNU_SOURCE,
>   dnl AC_MINIX. If people still use AC_AIX or AC_MINIX, they are out of luck.
>   AC_REQUIRE([AC_GNU_SOURCE])
>
>   AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])
> ])
>
> Would it be right to say that this should be changed in Gnulib,
> otherwise any project using that file with Gnulib will have errors
> from the new autoconf?

Yes, indeed.  All of the Gnulib and Autoconf Macro Archive macros need
to be checked for problems like this.  I'm cc:ing gnulib-bugs.

zw