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    SubjectRe: touch commands in Makefiles
    [Brendan Simon]
    > Why are header file touched in Makefiles ?

    Dependency reasons. Header files depend on whatever CONFIG options
    they reference, and this is implemented via proxy header files. Say
    you have foo.c which includes foo_bar.h which makes a reference to
    CONFIG_BAR. The correct dep tree would be

    foo.o: foo.c foo_bar.h CONFIG_BAR

    but, as it turned out, it was easier / more efficient to represent the
    tree as

    foo.o: foo.c foo_bar.h
    foo_bar.h: CONFIG_BAR

    This second tree is not strictly correct -- foo_bar.h does *not* in
    fact need to be rebuilt when CONFIG_BAR changes -- so the 'touch'
    commands are there to make it work correctly.

    If you don't like it (and most of us don't!), you should patch your
    tree with Keith Owens's 2.5 makefile structure, "kbuild-2.5". It fixes
    this problem (and many others). It is hoped that kbuild-2.5 will be
    merged with Linux 2.5 in the near future.

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      Last update: 2005-03-22 13:18    [W:0.020 / U:13.392 seconds]
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