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Chapter 8: Functions for Transforming Text 95

‘environment’

if variable was inherited from the environment provided to make.

‘environment override’

if variable was inherited from the environment provided to make, and is over-

riding a setting for variable in the makeﬁle as a result of the ‘-e’ option (see

Section 9.7 [Summary of Options], page 104).

‘file’

if variable was deﬁned in a makeﬁle.

‘command line’

if variable was deﬁned on the command line.

‘override’

if variable was deﬁned with an override directive in a makeﬁle (see Section 6.7

[The override Directive], page 68).

‘automatic’

if variable is an automatic variable deﬁned for the execution of the recipe for

each rule (see Section 10.5.3 [Automatic Variables], page 120).

This information is primarily useful (other than for your curiosity) to determine if you

want to believe the value of a variable. For example, suppose you have a makeﬁle foo that

includes another makeﬁle bar. You want a variable bletch to be deﬁned in bar if you

run the command ‘make -f bar’, even if the environment contains a deﬁnition of bletch.

However, if foo deﬁned bletch before including bar, you do not want to override that

deﬁnition. This could be done by using an override directive in foo, giving that deﬁnition

precedence over the later deﬁnition in bar; unfortunately, the override directive would

also override any command line deﬁnitions. So, bar could include:

ifdef bletch

ifeq "$(origin bletch)" "environment"

bletch = barf, gag, etc.

endif

If bletch has been deﬁned from the environment, this will redeﬁne it.

If you want to override a previous deﬁnition of bletch if it came from the environment,

even under ‘-e’, you could instead write:

ifneq "$(findstring environment,$(origin bletch))" ""

bletch = barf, gag, etc.

endif

Here the redeﬁnition takes place if ‘$(origin bletch)’ returns either ‘environment’ or

‘environment override’. See Section 8.2 [Functions for String Substitution and Analysis],

page 84.

8.11 The flavor Function

The flavor function, like the origin function, does not operate on the values of variables

but rather it tells you something about a variable. Speciﬁcally, it tells you the ﬂavor of a

variable (see Section 6.2 [The Two Flavors of Variables], page 60).

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