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* A primitive operation `dependencyClosure' to do automatic dependency

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determination (e.g., finding the header files dependencies of a C
  file) in Nix low-level builds automatically.

  For instance, in the function `compileC' in make/lib/default.nix, we
  find the header file dependencies of C file `main' as follows:

    localIncludes =
      dependencyClosure {
        scanner = file:
          import (findIncludes {
            inherit file;
          });
        startSet = [main];
      };

  The function works by "growing" the set of dependencies, starting
  with the set `startSet', and calling the function `scanner' for each
  file to get its dependencies (which should yield a list of strings
  representing relative paths).  For instance, when `scanner' is
  called on a file `foo.c' that includes the line

    #include "../bar/fnord.h"

  then `scanner' should yield ["../bar/fnord.h"].  This list of
  dependencies is absolutised relative to the including file and added
  to the set of dependencies.  The process continues until no more
  dependencies are found (hence its a closure).

  `dependencyClosure' yields a list that contains in alternation a
  dependency, and its relative path to the directory of the start
  file, e.g.,

    [ /bla/bla/foo.c
      "foo.c"
      /bla/bar/fnord.h
      "../bar/fnord.h"
    ]

  These relative paths are necessary for the builder that compiles
  foo.c to reconstruct the relative directory structure expected by
  foo.c.

  The advantage of `dependencyClosure' over the old approach (using
  the impure `__currentTime') is that it's completely pure, and more
  efficient because it only rescans for dependencies (i.e., by
  building the derivations yielded by `scanner') if sources have
  actually changed.  The old approach rescanned every time.
This commit is contained in:
Eelco Dolstra 2005-08-14 12:38:47 +00:00
parent 714b7256cd
commit 08c53923db
6 changed files with 147 additions and 30 deletions
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19
make/lib/default.nix
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@ -14,11 +14,13 @@ rec {
builder = ./compile-c.sh;
localIncludes =
if localIncludes == "auto" then
import (findIncludes {
main = toString main;
hack = __currentTime;
inherit cFlags;
})
dependencyClosure {
scanner = main:
import (findIncludes {
inherit main;
});
startSet = [main];
}
else
localIncludes;
inherit main;
@ -36,10 +38,11 @@ rec {
};
*/
findIncludes = {main, hack, cFlags ? ""}: stdenv.mkDerivation {
findIncludes = {main}: stdenv.mkDerivation {
name = "find-includes";
builder = ./find-includes.sh;
inherit main hack cFlags;
realBuilder = pkgs.perl ~ "bin/perl";
args = [ ./find-includes.pl ];
inherit main;
};
link = {objects, programName ? "program", libraries ? []}: stdenv.mkDerivation {