[mythtv] FYI: Recursive Make Considered Harmful

[Brad Allen]

The below is relevant to Myth.  Below abstract copied from
<URL:"http://WWW.PCUG.Org.Au/~millerp/rmch/recu-make-cons-harm.html">;
paper at <URL:"http://AEGIS.SourceForge.Net/auug97.pdf">:


                       Recursive Make Considered Harmful

                                 Peter Miller
                           millerp at canb.auug.org.au

Copyright (C) 1997 Peter Miller. All rights reserved.

This paper is available in PDF format.  [See above for paper link.]

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                                   ABSTRACT

    For large UNIX projects, the traditional method of building the
    project is to use recursive make. On some projects, this results
    in build times which are unacceptably large, when all you want to
    do is change one file. In examining the source of the overly long
    build times, it became evident that a number of apparently
    unrelated problems combine to produce the delay, but on analysis
    all have the same root cause.

    This paper explores an number of problems regarding the use of
    recursive make, and shows that they are all symptoms of the same
    problem. Symptoms that the UNIX community have long accepted as a
    fact of life, but which need not be endured any longer. These
    problems include recursive makes which take ``forever'' to work
    out that they need to do nothing, recursive makes which do too
    much, or too little, recursive makes which are overly sensitive to
    changes in the source code and require constant Makefile
    intervention to keep them working.

    The resolution of these problems can be found by looking at what
    make does, from first principles, and then analyzing the effects
    of introducing recursive make to this activity. The analysis shows
    that the problem stems from the artificial partitioning of the
    build into separate subsets. This, in turn, leads to the symptoms
    described. To avoid the symptoms, it is only necessary to avoid
    the separation; to use a single Makefile for the whole project.

    This conclusion runs counter to much accumulated folk wisdom in
    building large projects on UNIX. Some of the main objections
    raised by this folk wisdom are examined and shown to be
    unfounded. The results of actual use are far more encouraging,
    with routine development performance improvements significantly
    faster than intuition may indicate. The use of a single project
    Makefile is not as difficult to put into practice as it may first
    appear.