Re: [PATCH] build: use automake's new $(AM_V_GEN) and $(AM_V_at) variables

[Jim Meyering]

Ralf Wildenhues wrote:

> Hi Jim,
>
> Jim Meyering writes:
>> --- a/src/Makefile.am
>> +++ b/src/Makefile.am
>> @@ -290,26 +290,29 @@ editpl = sed -e 's,@''PERL''@,$(PERL),g'
>>
>>  BUILT_SOURCES += dircolors.h
>>  dircolors.h: dcgen dircolors.hin
>> -    @rm -f $@ address@hidden
>> -    $(PERL) -w -- $(srcdir)/dcgen $(srcdir)/dircolors.hin > address@hidden
>> -    @chmod a-w address@hidden
>> -    mv address@hidden $@
>> +    $(AM_V_GEN)
>> +    $(AM_V_at)rm -f $@ address@hidden
>> +    $(AM_V_at)$(PERL) -w -- $(srcdir)/dcgen $(srcdir)/dircolors.hin > 
>> address@hidden
>> +    $(AM_V_at)chmod a-w address@hidden
>> +    $(AM_V_at)mv address@hidden $@
>
> Thanks for using these.  Note the $(AM_V_GEN) will expand to the empty string
> with V=1 or --disable-silent-rules.  I am actually not sure whether any make
> implementation fails hard upon empty rule commands, but a couple of them will
> output a warning, such as FreeBSD:
>   $(AM_V_GEN) expands to empty string
>
> and AIX:
>   make: 1254-053 Command "$(AM_V_GEN)" expands to empty string.
>
> You might want to just prepend the $(AM_V_GEN) to the next command, without
> anything in-between.  We might want to document this better in automake.texi.

Hi Ralf,

How about making AM_V_GEN expand to ":;" rather than the empty string?
That would seem slightly more symmetric.
Fewer pitfalls for users, too.