bug#20077: automake / silent-rules / $(V)

[Pavel Raiskup]

On Wednesday 11 of March 2015 02:06:40 Mirko Vogt wrote:
> I just stumbled across an issue where a project fails to compile using
> automake and silent-rules with $V being set to sth. else other than '1'
> or '0'.
> 
> This is because of the following resulting Makefile code when using
> silent rules:
> 
> AM_V_P = $(am__v_P_$(V))
> am__v_P_ = $(am__v_P_$(AM_DEFAULT_VERBOSITY))
> am__v_P_0 = false
> am__v_P_1 = :
> 
> This breaks builds in environments such as e.g. the cross-compiling
> framework OpenWrt - which also uses $(V), however with values other than
> 1/0 (e.g. V=99, V={c,w,s}, etc.).

Its not ideal (dirty), but you can work-around that by specifying
'make AM_V_P=true' explicitly.  Or the project itself can do something
like

  $ cat Makefile.am | grep ^AM_V_P
  AM_V_P = test x0 = "x$(V)"

.. when the project is known to use $V for its own purposes.

> The way automake behaves here it claims that variable for its exclusive
> use. I don't mind automake using $(V), however if using such generic
> variable names, please don't make projects fail when $(V) is set to
> something other than 1 or 0.
> 
> My proposal would be to enable verbose output, if $(V) is set to
> anything but '0' and to disable otherwise ($V is unset / set to '0').

That would probably require changing the semantics of $AM_V_P a bit, as it
now was always ':' or 'false'.  But could be worth having fixed somehow.

Pavel