I am trying to determine what the the difference is between the "$" and "@" when used during expression evaluation (if that is the correct term). For instance, in the Makefile I am trying to understand there is the following expression

NO-DEBUG   := @(if $(DEBUG),,1)

Later, there is the following expression

NO-CHECKED  := $(if $(CHECKED),,1)

These seem to be doing the same thing, but I am not sure how the "$" and "@" might be affecting the evaluations. I couldn't find anything by searching for ":= @" or "= @" in my cursory google searches. Any insight? Why would one be used apposed to the other?

Thanks and regards, Mark


I've never seen and have no idea about @(expression) in GNU make. It would simply be left uninterpreted if used. I confirmed it by tests with GNU make 4.0. There seems no mention in the manual.

Regarding = and :=, you should read The Two Flavors of Variables in the reference manual. There's detailed explanation with examples.

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  • yaegashi, thanks for the response. My wording of my question wasn't the best as I was not looking for differences between "=" and ":=". My search started with ":= @", but yielded not results. So, I expanded the search to "= @" along with "gnu make" (in both cases). We are using v3.81, so I suspect your result will be the same with this version. I have no idea why it was used or if it was a mistake in the Makefile. – lordhog Jun 10 '15 at 0:02
  • @lordhog Ok, could you show that Makefile or tell the name of software that has it? – yaegashi Jun 10 '15 at 2:04
  • the Makefile comes from an internal project (not open source) file, so I can't share it. I had asked a few friends what it was, but best they thought it was something added for compatibility with another make utility. Thus, I was at a lost and posted this question. There were only two instances. One of which was the NO-DEBUG. – lordhog Jun 10 '15 at 2:35

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