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Suggestion for make manual

From: Sean Mahnken
Subject: Suggestion for make manual
Date: Fri, 3 Jan 2014 21:00:13 +0000

I came across a peculiar behavior while working with make.  If it is expected behavior, it would be worth documenting.  If it is not, a bug should be filed.


The following variable will never receive its default assignment:


# Set default for foo

export foo

foo ?= 5



It would appear that the export directive causes variables to be defined with an empty value, which renders the ?= assignment useless.  However, the following works fine:


# Set default for foo

export foo ?= 5


This may be common knowledge for some folks, but I struggled with it for a while.  I believe it would be worth noting in section 5.7.2 and/or 6.2 of the make manual.


Thanks –

Sean Mahnken

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