Invalid syntax in Makefile?

[rpdelaney]

Looking at the Makefile again, this looks like it's invalid shell code:

export XDG_DATA_HOME ?= $${$$HOME/.local/share}

Based on my understanding, I would expect:

export XDG_DATA_HOME ?= $(HOME)/.local/share

However, I'm not a GNU Make guru. Is there some make magic going on here?

[rpdelaney]

@ahmedelgabri Would you be so kind as to weigh in on this?

[ahmedelgabri]

@rpdelaney I don't remember exactly why I did it this way. But I think the first one evaluates the whole expression which contains the $HOME variable. While the second one only evaluates the $(HOME) part.

I'm on phone so I can't check now.

[rpdelaney]

I did a little more research and you're right. This is just my ignorance of GNU Make showing. Sorry for the false alarm!

[rpdelaney]

Okay, I see the problem now. This actually fails to build when $XDG_DATA_HOME is not set:

$ unset XDG_DATA_HOME
$ make install
/bin/sh: ${$HOME/.local/share}: bad substitution
make: *** [install] Error 1