File: make.info,  Node: Pattern-specific,  Next: Suppressing Inheritance,  Prev: Target-specific,  Up: Using Variables

6.12 Pattern-specific Variable Values
=====================================

In addition to target-specific variable values (*note Target-specific
Variable Values: Target-specific.), GNU 'make' supports pattern-specific
variable values.  In this form, the variable is defined for any target
that matches the pattern specified.

   Set a pattern-specific variable value like this:

     PATTERN ... : VARIABLE-ASSIGNMENT
   where PATTERN is a %-pattern.  As with target-specific variable
values, multiple PATTERN values create a pattern-specific variable value
for each pattern individually.  The VARIABLE-ASSIGNMENT can be any valid
form of assignment.  Any command line variable setting will take
precedence, unless 'override' is specified.

   For example:

     %.o : CFLAGS = -O

will assign 'CFLAGS' the value of '-O' for all targets matching the
pattern '%.o'.

   If a target matches more than one pattern, the matching
pattern-specific variables with longer stems are interpreted first.
This results in more specific variables taking precedence over the more
generic ones, for example:

     %.o: %.c
             $(CC) -c $(CFLAGS) $(CPPFLAGS) $< -o $@

     lib/%.o: CFLAGS := -fPIC -g
     %.o: CFLAGS := -g

     all: foo.o lib/bar.o

   In this example the first definition of the 'CFLAGS' variable will be
used to update 'lib/bar.o' even though the second one also applies to
this target.  Pattern-specific variables which result in the same stem
length are considered in the order in which they were defined in the
makefile.

   Pattern-specific variables are searched after any target-specific
variables defined explicitly for that target, and before target-specific
variables defined for the parent target.