make: Suppressing Inheritance
6.13 Suppressing Inheritance
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As described in previous sections, 'make' variables are inherited by
prerequisites. This capability allows you to modify the behavior of a
prerequisite based on which targets caused it to be rebuilt. For
example, you might set a target-specific variable on a 'debug' target,
then running 'make debug' will cause that variable to be inherited by
all prerequisites of 'debug', while just running 'make all' (for
example) would not have that assignment.
Sometimes, however, you may not want a variable to be inherited. For
these situations, 'make' provides the 'private' modifier. Although this
modifier can be used with any variable assignment, it makes the most
sense with target- and pattern-specific variables. Any variable marked
'private' will be visible to its local target but will not be inherited
by prerequisites of that target. A global variable marked 'private'
will be visible in the global scope but will not be inherited by any
target, and hence will not be visible in any recipe.
As an example, consider this makefile:
EXTRA_CFLAGS =
prog: private EXTRA_CFLAGS = -L/usr/local/lib
prog: a.o b.o
Due to the 'private' modifier, 'a.o' and 'b.o' will not inherit the
'EXTRA_CFLAGS' variable assignment from the 'prog' target.
Info Catalog
make: Pattern-specific
make: Using Variables
make: Special Variables