Re: Recreate depfiles when regenerating Makefiles

[Raja R Harinath]

Hi,

Tom Tromey <address@hidden> writes:

>>>>>> "Hari" == Raja R Harinath <address@hidden> writes:
>
> Hari> Akim once suggested adding a facility to hook commands to files
> Hari> listed in AC_CONFIG_FILES.
>
> The problem with this idea is that the information about which files
> is known when automake is run, not when autoconf is run.

I meant it this way:

  AC_CONFIG_FILES([foo/Makefile])

and elsewhere, some _AM_* macro generates

  AC_CONFIG_FILE_HOOK([foo/Makefile], 
  [# same commands as run for 'depfiles' AC_CONFIG_COMMAND
  ])

(Though, IIRC, Akim wanted this functionality as part of AC_CONFIG_COMMAND).

> Hari> Anyway, till that date, it may make sense to handle this somewhat
> Hari> hackily.  One issue with generating the above command is that it is
> Hari> safe to invoke the 'depfiles' CONFIG_COMMAND only in some cases, and
> Hari> at the time 'automake' emits the Makefile regeneration code, it
> Hari> doesn't know if it's safe yet.  So, here goes:
>
> I think it is always safe to run the depfiles command.  The command
> itself looks to see if the file it is modifying is an automake
> output.  So I think it is ok to simply always run the `depfiles'
> rule.

No.  It is currently safe only if one of the AC_PROG_CC or AC_PROG_CXX
commands is present in configure.in, thanks to the shenanigans in 
init.m4.  That's why I went through the extra step.

Thanks.

- Hari
-- 
Raja R Harinath ------------------------------ address@hidden
"When all else fails, read the instructions."      -- Cahn's Axiom
"Our policy is, when in doubt, do the right thing."   -- Roy L Ash