Re: Possible bug with pattern-specific variables

[Markus F.X.J. Oberhumer]

Thanks for trying to help me understanding this issue.

### BEGIN Makefile
FOO +=
build/%: BAR +=
build/release: ; @echo "FOO='$(FOO)' BAR='$(BAR)'"
### END


# changes BAR in unexpected ways; see 1) and 2) below
$ make FOO=X BAR=Y

vs.

# this works as expected
$ env FOO=X BAR=Y make


1) how can the expression "BAR +=" duplicate the contents of BAR ?

2) and I had expected that BAR is immutable anyway, just like FOO

~Markus



On 2023-09-27 16:51, Bahman Movaqar wrote:
> I certainly tried out your snippet the first time before replying 🙂
> 
> To my mind, what you're missing is the fact that `build/% : BAR +=' is
> evaluated as part of `build/release'.
> 
> It is no different than the following snippet from the manual:
> 
> 🙶
> objects = foo.o bar.o
> foo.o : defs.h
> bar.o : defs.h test.h
> $(objects) : config.h
> 🙸
> 
> In the above snippet, last line is not recipe for for `$(objects)'. 
> However, it does mutate its prerequisites.
> 
> In the same vein, line #2 of your snippet, while not being a recipe for
> `build/release', updates its prerequisites (in this case just a
> variable.)
> 
> See https://www.gnu.org/software/make/manual/make.html#Multiple-Rules
> 
> Does that make sense?
> 

-- 
Markus Oberhumer, <markus@oberhumer.com>, http://www.oberhumer.com/