CODEWITHSUNDEEP
makefilegnu-make
aimass
aimass

Reputation: 418

GNU Make: Test if either OR variables are null or undefined

As I understand it $(and should short circuit and return "" if either VAR1 OR VAR2 is null or undefined. This should make the ifeq true and print the message. Otherwise if both variables have values it should return the value of VAR2 which is obviously not "" making the ifeq evaluation false and not printing the message.

It's not working. What am I missing?

ifeq ($(and $(VAR1),$(VAR2)), "")
$(info *************************************)
$(info *        To avoid prompts set       *)
$(info *          VAR1 and VAR2            *)
$(info *       prior to running make       *)
$(info *************************************)
endif

Upvotes: 0

Views: 389

Answers (1)

MadScientist
MadScientist

Reputation: 100836

Yes. Basically: all arguments have contents, then the expansion is the contents of the last one. Otherwise, the expansion is empty.

Note, none of these situations result in the expansion being the value "", which is not empty it's two " characters in a row. Make doesn't do anything special with quotes: they are just like any other character. So, saying ifeq (,"") is always false. You don't want to compare a string with "" unless you want to check if the string literally contains two double-quote characters in a row.

So I think (if I understand you correctly) you want:

ifeq ($(and $(VAR1),$(VAR2)),)

Upvotes: 1

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