Re: [PATCH 4/6] autoregen.py: Use autoreconf in most GCC directories

[Simon Marchi <simark@simark.ca>]

On 2024-04-16 10:47, Christophe Lyon wrote:
>> If I call `aclocal` without args in gcc/gcc, it re-generates aclocal.m4
>> fine, because it got the include path info from configure.ac.  If I
>> remove the `AC_CONFIG_MACRO_DIRS` line from gcc/gcc/configure.ac and run
>> aclocal.m4, then I am missing a bunch of m4 files in the resulting
>> aclocal.m4.  If I remove the `ACLOCAL_AMFLAGS` variable from
>> gcc/gcc/Makefile.am, it has no effect on `aclocal`.  That variable only

Sorry, I wrote Makefile.am here, it should be Makefile.in.

>> exists for the benefit of the Makefile rule that regenerates aclocal.m4,
>> lower in Makefile.am.  But I would argue that it's unnecessary, since
>> that info is encoded in configure.ac, so the rule could call aclocal
>> without any -I args.
> 
> Of course: aclocal does NOT read Makefile.am, but autoreconf does.

Ok, I wasn't aware of autoreconf getting flags for aclocal from
ACLOCAL_AMFLAGS in Makefile.am, now I see it in the docs.  But it seems
to me like autoreconf will "just work" in most cases then:

 - for directories with a Makefile.am, autoreconf will read the -I flags
   specified in Makefile.am/ACLOCAL_AMFLAGS and pass them to aclocal.
 - for directories without a Makefile.am (like GDB), autoreconf will
   call aclocal without -I flags, but aclocal will use the include paths
   specified in configure.ac/AC_CONFIG_MACRO_DIRS.

> So what I noticed for the 'gcc' subdir is that autoreconf will
> generate the same contents but also print a few warnings.
> This is because when calling aclocal with some -I flags, the contents
> of those included .m4 files is taken into account before scanning
> configure.ac, so macros like AM_PATH_PROG_WITH_TEST are defined before
> being used, while when using autoreconf (thus calling aclocal without
> any -I flag), those .m4 files are processed later, leading to warnings
> that AM_PATH_PROG_WITH_TEST is "not found in library". IIUC, there's
> an iterative process which means that things are re-assessed later.
> 
> So.... it seems it's not a real problem to use autoreconf as you
> suggest, but we'll see such warnings in the buildbot logs (not causing
> errors IIUC).

I don't really know how this is supposed to work then, it seems
illogical to me.  aclocal recommends using AC_CONFIG_MACRO_DIRS:

  https://www.gnu.org/software/automake/manual/html_node/Local-Macros.html

So it seems to me like it should consider the macros found in these
directories when processing the rest of the files...

Simon