Re: How to properly define package-wide flags.

[Ralf Wildenhues]

Hello Benoit,

* Benoit Sigoure wrote on Thu, Nov 16, 2006 at 08:03:57AM CET:
> 
> Akim's idea of AM_*FLAGS is that they are not meant to be defined in
> configure.ac but in Makefile.ams. His approach is to AC_SUBST([MY_*FLAGS],
> [-package-wide-flags]) and then have a common.mk (say at top-level) which
> does AM_*FLAGS = $(MY_*FLAGS) and then include that common.mk everywhere it's
> required.

Advantages of your approach:
- less to type, less to remember, thus less error-prone.

Advantages of Akim's approach:
- more flexible: when later you find out you need to apply MY_*FLAGS
  only to a subset of the code, and MYOTHER_*FLAGS to some other subset.
  You could override the setting in common.mk after including it, or
  just not include it in all Makefile.am files.
- there may be other independent reasons why you would want or need a
  common.mk that shares code for all or most Makefile.am files.

> According to him, defining package-wide AM_*FLAGS could possibly clash with
> that already defined in Makefile.ams.

If you both substitute it and set it in a Makefile.am, the latter wins
(in that Makefile.am, of course).  No clash here, but of course the
order is important.

> He also argues that when defining target_specific_*FLAGS, the
> corresponding AM_*FLAGS aren't automatically included.

There is no problem with
  target_CFLAGS = $(AM_CFLAGS) --moreflags $(even_more_flags)

Also, the issue is the same for your and his case, so really this isn't
an argument until you need a split in the form of
  AM_CFLAGS = $(A) $(B)
  target_CFLAGS = $(A) $(something_other_than_B)

IMHO it's really a matter of taste.  Do whatever fits your project best.
I like to avoid per-target flags if I can, because it helps keep the
size of Makefile.in down.  But that's only a very minor point.

Cheers,
Ralf