Hi,
I would suggest to mention the current behavior in the manual, instead of
making $(value ...) to emit a warning. The main motivation is backward
compatibility.
In our project we widely use $(value N) to get arguments of 'call' that are
assumed to be optional without raising a warning (I've just found about 100
lines where we use it to suppress the warning). And we also always use make
with '--warn-undefined-variables' flag too.
For example,
# Args:
# 1. A list to convert into a PATH variable.
# 2. (Optional) path separator to use. When empty, defaults to a colon.
PATHIFY = \
$(subst $(space),$(or $(value 2),$(colon)),$(strip $1))
This allows one to use $(call PATHIFY,foo bar) as well as $(call
PATHIFY,bar baz,;).
Without using the 'value' function I would have to write something like:
$(subst $(space),$(if $(and $(filter-out undefined,$(flavor
2)),$2),$2,$(colon)),$(strip $1))
The latter looks ugly and it is also much slower if the function is assumed
to be called often. And all these drawbacks would be needed only to
suppress a warning.
Well, in other word, I think about 'value' function as a kind of an
introspection facility. It is much like as 'flavor' or 'origin' functions,
which do not generate a warning for undefined variables. So I wish to leave
the current behavior as is and to describe it in the manual.
2012/3/14 R. Diez <rdiezmail-openr...@yahoo.de>
> Hi all:
>
> Writing makefiles is hard enough, so I always enable option
> --warn-undefined-variables whenever I can.
>
> I have recently realised that in GNU Make 3.81 the $(value ...) function
> does not warn as expected. That is, if I run this example makefile:
>
>
> VAR_NAME := UNDEFINED_VARIABLE
>
> all:
> echo "$(UNDEFINED_VARIABLE)"
> echo "$($(VAR_NAME))"
> echo "$(value $(VAR_NAME))"
>
>
> I get the following output:
>
> Makefile:24: Warnung: undefinierte Variable »UNDEFINED_VARIABLE«
> Makefile:24: Warnung: undefinierte Variable »UNDEFINED_VARIABLE«
> echo ""
> echo ""
> echo ""
>
>
> Is this an oversight? The manual does not mention any exceptions for
> --warn-undefined-variables, and I wish that $(value ...) warned too.
>
>
> Please copy me on the answers, as I'm not subscribed to this list.
>
> Thanks,
> R. Diez
>
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> https://lists.gnu.org/mailman/listinfo/bug-make
>
--
Best regards,
Eldar Sh. Abusalimov
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