On Sat, 2024-01-27 at 20:27 +0100, Basile Starynkevitch wrote:
> > It would be great if you could provide examples where these would
> > be
> > useful, especially examples that are not already covered by the
> > output
> > of the -p option to GNU Make.
>
> make -p don't show (unfortunately) the line number in makefiles.
> Alternatively, a runtime option for make -p (perhaps
> --show-line-numbers) would be nice.
It definitely DOES show line numbers. For example for a variable
definition:
# makefile (from 'Makefile', line 361)
PACKAGE_NAME = GNU Make
and for a rule definition:
all: alloca.h
# ...
# recipe to execute (from 'Makefile', line 490):
$(MAKE) $(AM_MAKEFLAGS) all-recursive
> > I'm not saying we shouldn't introduce these, although I think you
> > misunderstand how tricky it would be to use them (for example, if
> > you set:
> >
> > FOO = $(__LINE__)
>
> This would be expanded at Makefile parsing time. Not at function
> invocation time.
I'm not sure what you mean by "this". It would be helpful to my
understanding if you used the example I provided and showed what value
you expected BAR to have: 1 or 3? Then I could be sure I understood
what you meant.
Macros and functions in recursive variable assignments ("=") are not
expanded when the variable is defined. They are expanded when the
variable is referenced. For example if you have:
bar = 1
FOO = $(bar)
bar = 2
all: ; @echo $(FOO)
then the output will be "2", not "1", because $(bar) is not expanded
when FOO is defined, it's expanded when $(FOO) is expanded (in the
recipe, in this example).
Are you suggesting that $(__LINE__) would somehow be a special case and
NOT work like this? So if I have:
bar = 1
FOO = $(bar) $(__LINE__)
bar = 2
all: ; @echo $(FOO)
the output I got would be "2 2" instead of "2 4"?
In other words, make would parse the value of FOO looking for
references to the special variables __LINE__ and __FILE__ and expand
only those, but not other macros or functions?
> If I started to implement it, I would add
>
> FT_ENTRY ("__LINE__", 0, 0, 0, func__LINE__),
>
> in GNU make's src/function.c file.
This would almost certainly not do what you want.
> So my intuition is that this feature is easy to implement.
I don't think you're correct about that. But any discussion of the
implementation details is premature: the behavior must be defined
first.
--
Paul D. Smith <psm...@gnu.org> Find some GNU make tips at:
https://www.gnu.org http://make.mad-scientist.net
"Please remain calm...I may be mad, but I am a professional." --Mad
Scientist
