Hello.
Geoff Clare wrote in
<20211220133200.GA25606@localhost>:
|Robert Elz wrote, on 18 Dec 2021:
|> bsd make (bmake) has a couple of macros (the doc calls what are
|> macros here variables, but they are the same thing), which default to
|> being unset, which can be set in the environment or command line,
|> but which cannot be set in any Makefile, as they alter the interpretation
|> of makefiles (slightly). That is, if they are going to be defined, that
|> needs to have happened before the first makefile line is read.
|> They are used (expanded) in makefiles quite commonly.
|>
|> For that to work, no rule requiring variables to be always set in the
|> Makefile before being expanded is possible
|
|No such rule is being proposed. The error is only allowed if
|the macro is expanded while unset. If it is set, it makes no
|difference how it was set.
|
|> The += is effectively shorthand for (not possible in make I think)
|> MACRO= ${MACRO} string
|> an so is effectively expanding the otherwise potentially unset MACRO
|> before altering it. Any implementation which generated an error on
|> an expansion of an unset macro would need to generate an error for
|> this usage (assuming MACRO was unset previously) as well.
|
|Thank you for pointing that out. We should revisit the proposed
|changes to allow this error as well.
Now that it starts to affect me.. :)
I do not think the proposal reflects practice.
For example CRUX-Linux has a /etc/pkgmk.conf where people can
define $CFLAGS, $CXXFLAGS, etc., also things like
export JOBS=$(nproc)
export MAKEFLAGS="-j $JOBS"
It is processed by the shell before the actual package is build.
I personally set things in my environment, $CFLAGS for example.
These things are picked up by most build processes automatically
ever since i consciously look at that.
all:
echo CFLAGS=$(CFLAGS)
->
echo CFLAGS=-O1 -g
CFLAGS=-O1 -g
or even
CFLAGS+=-Weven-more-noise
all:
echo CFLAGS=$(CFLAGS)
->
echo CFLAGS=-O1 -g -Weven-more-noise
CFLAGS=-O1 -g -Weven-more-noise
This would vanish with the proposal:
CFLAGS=
CFLAGS+=-Weven-more-noise
all:
echo CFLAGS=$(CFLAGS)
->
echo CFLAGS=-Weven-more-noise
CFLAGS=-Weven-more-noise
It even becomes impossible to get the same effect that is used in
the wild, as Robert Elz already said, specifying 'make
CFLAGS="$CFLAGS"' on the command line hard-sets CFLAGS in the
makefile, and the += never comes into play.
--steffen
|
|Der Kragenbaer, The moon bear,
|der holt sich munter he cheerfully and one by one
|einen nach dem anderen runter wa.ks himself off
|(By Robert Gernhardt)
