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Chapter 3: Writing Makeﬁles 17

immediate != immediate

define immediate

deferred

endef

define immediate =

deferred

endef

define immediate ?=

deferred

endef

define immediate :=

immediate

endef

define immediate ::=

immediate

endef

define immediate +=

deferred or immediate

endef

define immediate !=

immediate

endef

For the append operator, ‘+=’, the right-hand side is considered immediate if the variable

was previously set as a simple variable (‘:=’ or ‘::=’), and deferred otherwise.

For the shell assignment operator, ‘!=’, the right-hand side is evaluated immediately and

handed to the shell. The result is stored in the variable named on the left, and that variable

becomes a simple variable (and will thus be re-evaluated on each reference).

Conditional Directives

Conditional directives are parsed immediately. This means, for example, that automatic

variables cannot be used in conditional directives, as automatic variables are not set until

the recipe for that rule is invoked. If you need to use automatic variables in a conditional

directive you must move the condition into the recipe and use shell conditional syntax

instead.

Rule Deﬁnition

A rule is always expanded the same way, regardless of the form:

immediate : immediate ; deferred

deferred

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Roland Ver. 4.5 Información técnica Pagina 27