Pattern-specific (GNU make)
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6.12 Pattern-specific Variable Values
In addition to target-specific variable values (see Target-specific Variable Values), 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.
