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Gary Holt > makepp-1.19 > makepp_extending


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makepp_extending -- How to extend makepp using perl


Makepp internally is flexible enough so that by writing a little bit of perl code, you can add functions or do a number of other operations.

General notes on writing perl code to work with makepp

Each makefile lives in its own package. Thus definitions in one makefile do not affect definitions in another makefile. A common set of functions including all the standard textual manipulation functions is imported into the package when it is created.

Makefile variables are stored as perl scalars in that package. (There is an exception to this: automatic variables and the default value of variables like CC are actually implemented as functions with no arguments.) Thus any perl code you write has access to all makefile variables, and any global variables you set can be accessed from the makefile.

Makepp cd's to the directory containing the makefile before executing any of your perl code.

Adding new textual functions

You can add a new function to makepp's repertoire by simply defining a perl subroutine of the same name but with a prefix of f_. For example:

    sub f_myfunc {
      my $argument = $_[0];     # Name the arguments.
      .. do something here
      return $return_value;
    XYZ := $(my_func my func arguments)

The first argument to the function is the remaining text in the function invocation after the function name. You'll have to split it into words yourself if that's what you want. There are other arguments, but they are pretty specific to makepp's internals and for most applications you shouldn't need to use them.

The function should return a scalar string (not an array) which is then inserted into the text at that point.

If your function encounters an error, it should die using the usual perl die statement. This will be trapped by makepp and an error message displaying the file name and the line number of the expression causing the error will be printed out.

There are essentially no limits on what the function can do; you can access the file, run shell commands, etc.

At present, expressions appearing in dependencies and in the rule actions are expanded once while expressions appearing in targets are expanded twice, so be careful if your function has side effects and is present in an expression for a target.


This document is not finished yet. It will soon cover how to control makepp's signature mechanism and also how to write your own scanners for include files and things like that.

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