Possible bug in Make's target-specific variable behavior

[Nicholas Clark]

Hi all,

I was experimenting with Make today, and I noticed a possible bug in Make's
target-specific variable handling.

>From the GNU Make manual (
https://www.gnu.org/software/make/manual/html_node/Target_002dspecific.html#Target_002dspecific),
I'd expect that I could combine "export" and "private" on the same
target-specific variable, in order to get environment variables local to a
single recipe.

But when I try it out, I see the variable in the target's dependencies as
well - exactly the behavior that "private" is supposed to block.

Here's an example Makefile that shows the problem.

#----------------------------------------#

default: noexport export
.RECIPEPREFIX = >

noexport_dep:
> @echo "$@: TEST_VALUE=[$(TEST_VALUE)]"

noexport: private TEST_VALUE=HELLO

noexport: noexport_dep
> @echo "$@: TEST_VALUE=[$(TEST_VALUE)]"

##

export_dep:
> @echo "$@: TEST_VALUE=[$$TEST_VALUE]"

export: private export TEST_VALUE=HELLO

export: export_dep
> @echo "$@: TEST_VALUE=[$$TEST_VALUE]"

#----------------------------------------#

>From the GNU Make manual, I'd expect to see this output:

user@hostname$ make
noexport_dep: TEST_VALUE=[]
noexport: TEST_VALUE=[HELLO]
export_dep: TEST_VALUE=[]
export: TEST_VALUE=[HELLO]

Instead, I see this output:

user@hostname$ make
noexport_dep: TEST_VALUE=[]
noexport: TEST_VALUE=[HELLO]
export_dep: TEST_VALUE=[HELLO]
export: TEST_VALUE=[HELLO]

Any thoughts on this? Is this a bug, or did I misinterpret the Make manual?

-Nick