The second patch fixes this second issue.

However, the following example still fails, even with the attached patch applied.

$ cat makefile
all:; @echo hello=$$hello
hello=sun
dummy: hello?=world

$ hello=moon  make
hello=

I user reported a bug here

https://lists.gnu.org/archive/html/bug-make/2020-10/msg00001.html


Hi,

I just got a build failure in lz4.  I've isolated it and made a minimal test
case, see below.

This is on GNU Guix on a x86_64 machine.

The reason is that apparently one Makefile rule can unwittingly change how
another unrelated rule functions, IF a submake is involved.

To reproduce:

$ cat Makefile

all:
        $(MAKE) -C foo all

dummy: CFLAGS ?= bar
dummy:

$ cat foo/Makefile

CFLAGS ?= internal

all:
        echo $(CFLAGS)

Expected behavior:

$ CFLAGS=ok make
make -C foo all
make[1]: Entering directory 'foo'
echo ok
ok
make[1]: Leaving directory 'foo'

Actual behavior:

$ CFLAGS=ok make
make -C foo all
make[1]: Entering directory 'foo'
echo internal
internal
make[1]: Leaving directory 'foo'

BR,
   Danny Milosavljevic