Re: [sr #111007] autoconf 2.72 warning: file 'version.m4' included several times

[Nick Bowler]

On 2024-01-13 03:26, Румен Петров wrote:
> autoconf 2.72 is first release that prints warning:
> configure.ac:2: warning: file 'version.m4' included several times

The warning here is erroneous and happens now because Autoconf-2.72's
m4sugar.m4 (which is used under the hood basically everywhere) now
includes an expansion of m4_sinclude([version.m4]).

Autoconf implements this warning with a very simplisic check for whether
a file is actually included multiple times: it defines the m4_include
and m4_sinclude macros which record the argument any time they are used,
checking if either was ever called with that argument before.

Now, m4sugar does not _actually_ include your version.m4, because the
Autoconf build/installation process generates an m4 "frozen state" file
(m4sugar.m4f) where the file inclusion is already done using version.m4
from Autoconf's source code, and this is what actually gets used when
you run autoconf.  However, the frozen state *does* include the record
that m4_sinclude was expanded previously with the version.m4 argument.

Probably we could fix this problem by changing m4sugar.m4 to not use
the m4_sinclude.  It could use m4_builtin([sinclude], [version.m4])
instead which would then not expose the record of internal inclusions
to the user like this.

To work around the warning in autoconf-2.72, you can change the spelling
of version.m4 to something functionally equivalent, for example:

  m4_include([./version.m4])

You can also just go in and delete the indication that Autoconf uses
to produce this warning, for example:

  m4_builtin([undefine], [m4_include(version.m4)])

Incidentally, while not relevant to your example, Autoconf 2.72 also
installs its own version.m4 file to the global m4 include search path,
so if you were previously using M4PATH or autoconf's -I option to locate
a file with this name then actually m4_include([version.m4]) will pick
up the one shipped with Autoconf instead of what probably anyone would
actually want to happen in this scenario.

Cheers,
  Nick

[sr #111007] autoconf 2.72 warning: file 'version.m4' included several times

[Румен Петров]

URL:
  

 Summary: autoconf 2.72 warning: file 'version.m4' included
several times
   Group: Autoconf
   Submitter: rpetrov
   Submitted: Sat 13 Jan 2024 08:26:06 AM UTC
Priority: 5 - Unprioritized
Severity: 2 - Minor
  Status: None
 Privacy: Public
 Assigned to: None
Originator Email: 
 Open/Closed: Open
 Discussion Lock: Any
Operating System: None


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Follow-up Comments:


---
Date: Sat 13 Jan 2024 08:26:06 AM UTC By: Румен Петров 
Sample version:
$ cat > version.m4 < configure.ac 

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