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11.2 Implicit Rule for Archive Member Targets

Recall that a target that looks like `a(m)' stands for the member named m in the archive file a.

When make looks for an implicit rule for such a target, as a special feature it considers implicit rules that match `(m)', as well as those that match the actual target `a(m)'.

This causes one special rule whose target is `(%)' to match. This rule updates the target `a(m)' by copying the file m into the archive. For example, it will update the archive member target `foo.a(bar.o)' by copying the file `bar.o' into the archive `foo.a' as a member named `bar.o'.

When this rule is chained with others, the result is very powerful. Thus, `make "foo.a(bar.o)"' (the quotes are needed to protect the `(' and `)' from being interpreted specially by the shell) in the presence of a file `bar.c' is enough to cause the following commands to be run, even without a makefile:

 
cc -c bar.c -o bar.o
ar r foo.a bar.o
rm -f bar.o

Here make has envisioned the file `bar.o' as an intermediate file. See section Chains of Implicit Rules.

Implicit rules such as this one are written using the automatic variable `$%'. See section Automatic Variables.

An archive member name in an archive cannot contain a directory name, but it may be useful in a makefile to pretend that it does. If you write an archive member target `foo.a(dir/file.o)', make will perform automatic updating with this command:

 
ar r foo.a dir/file.o

which has the effect of copying the file `dir/file.o' into a member named `file.o'. In connection with such usage, the automatic variables %D and %F may be useful.

11.2.1 Updating Archive Symbol Directories  How to update archive symbol directories.


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