Enhancing automake support for silent-rules

[Darren Garvey]

Hi all,

I've been trying to make a large automake-generated project I work on build
quieter. While there is some support for "silent-rules", there are several
places where automake templates* don't silence themselves, which I'd like
to rectify.

I have made several changes locally which helps a lot and I'd like to
prepare a patch. Since I've not hacked on automake before I may need some
guidance on conventions as not all of them are obvious to me.

To make a rule conditionally silent, I use $(AM_V_at) in _my_ projects, but
automake sources itself have %SILENT% which seems to be equivalent, IIUC.
Is %SILENT% preferred?

The HACKING file says:

> * For install and uninstall rules, if a loop is required, it should be
>   silent.  Then the body of the loop itself should print each "important"
>   command it runs.  The printed commands should be preceded by a single
>   space.

This means there are several places in the templates that have a long
multi-line rule that is itself silent, but includes one or more "echo"s.
One idea was to define a local function such as:

am_echo() { echo "$@" >/dev/null; }

and then define $(AM_V_echo) that conditionally used either "echo" or
"am_echo". This feels a bit ugly but it should be minimally intrusive.
Perhaps there's a more canonical way to do this using some existing
automake feature. I imagine anyone working on the silent-rules support may
have already thought about this and may have a superior alternative
suggestion....

Cheers,

Darren

* I'm calling the files under lib/am/ templates.