Re: Turning warning into errors

[Kaz Kylheku (gmake)]

On 2019-05-02 18:31, Sébastien Hinderer wrote:
> Dear Duane,
>
> Many thanks for your response!
>
> You are right, the code is rather straightforward and at the same time 
> I
> find it clever! In particular, I like the fact that, because of the
> options you are using, you don't need to use grep to figure out whether
> there are warnings or not. We would have to work quite a bit to reach
> this state but it's interesting to know the trick so I am very grateful
> to you that you shared your solution with me!

Hmm? It seems you don't have to work hard at all; you can just run
your existing Makefile with those same options to get an immediate 
benefit:

  make --warn-undefined-variables --silent --dry-run clean ... 2>&1 > 
/dev/null

and check that the output is empty.  Duane has just put in a convenience
target to do this via "make check_undefined_vars".

Let's try it in a project of mine:

  ~/txr$ make --warn-undefined-variables --silent --dry-run clean 2>&1  
> /dev/null
  Makefile:32: warning: undefined variable `CFLAGS'
  Makefile:33: warning: undefined variable `EXTRA_FLAGS'
  Makefile:37: warning: undefined variable `LDFLAGS'
  Makefile:38: warning: undefined variable `EXTRA_LDFLAGS'

Good. These should be undefined; if the user sets these, we use them.
Glad to see there are no others. :)

The "make self_test_check_undefined_vars" target just triggers an 
undefined
variable condition (the expression $(nothing at all)) to provide a basic
proof that it's doing something.

This can be integrated in a simpler form without the self-test stuff, 
and
you might not be interested in the other kinds of checks that are in 
that
file that add to its complexity.