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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.
63 lines
1.4 KiB
Nix
63 lines
1.4 KiB
Nix
rec {
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# Should point at your Nixpkgs installation.
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pkgPath = ./pkgs;
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pkgs = import (pkgPath + /system/all-packages.nix) {};
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stdenv = pkgs.stdenv;
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compileC = {main, localIncludes ? "auto", cFlags ? "", sharedLib ? false}:
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stdenv.mkDerivation {
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name = "compile-c";
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builder = ./compile-c.sh;
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localIncludes =
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if localIncludes == "auto" then
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dependencyClosure {
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scanner = main:
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import (findIncludes {
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inherit main;
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});
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startSet = [main];
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}
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else
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localIncludes;
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inherit main;
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cFlags = [
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cFlags
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(if sharedLib then ["-fpic"] else [])
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];
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};
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/*
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runCommand = {command}: {
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name = "run-command";
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builder = ./run-command.sh;
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inherit command;
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};
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*/
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findIncludes = {main}: stdenv.mkDerivation {
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name = "find-includes";
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realBuilder = pkgs.perl ~ "bin/perl";
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args = [ ./find-includes.pl ];
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inherit main;
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};
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link = {objects, programName ? "program", libraries ? []}: stdenv.mkDerivation {
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name = "link";
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builder = ./link.sh;
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inherit objects programName libraries;
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};
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makeLibrary = {objects, libraryName ? [], sharedLib ? false}:
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# assert sharedLib -> fold (obj: x: assert obj.sharedLib && x) false objects
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stdenv.mkDerivation {
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name = "library";
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builder = ./make-library.sh;
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inherit objects libraryName sharedLib;
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};
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}
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