lix/make/lib/compile-c.sh
Eelco Dolstra 08c53923db * A primitive operation `dependencyClosure' to do automatic dependency
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.
2005-08-14 12:38:47 +00:00

75 lines
1.9 KiB
Bash

. $stdenv/setup
mainName=$(basename $main | cut -c34-)
echo "compiling \`$mainName'..."
# Turn $localIncludes into an array.
localIncludes=($localIncludes)
# Determine how many `..' levels appear in the header file references.
# E.g., if there is some reference `../../foo.h', then we have to
# insert two extra levels in the directory structure, so that `a.c' is
# stored at `dotdot/dotdot/a.c', and a reference from it to
# `../../foo.h' resolves to `dotdot/dotdot/../../foo.h' == `foo.h'.
n=0
maxDepth=0
for ((n = 0; n < ${#localIncludes[*]}; n += 2)); do
target=${localIncludes[$((n + 1))]}
# Split the target name into path components using some IFS magic.
savedIFS="$IFS"
IFS=/
components=($target)
depth=0
for ((m = 0; m < ${#components[*]}; m++)); do
c=${components[m]}
if test "$c" = ".."; then
depth=$((depth + 1))
fi
done
IFS="$savedIFS"
if test $depth -gt $maxDepth; then
maxDepth=$depth;
fi
done
# Create the extra levels in the directory hierarchy.
prefix=
for ((n = 0; n < maxDepth; n++)); do
prefix="dotdot/$prefix"
done
# Create symlinks to the header files.
for ((n = 0; n < ${#localIncludes[*]}; n += 2)); do
source=${localIncludes[n]}
target=${localIncludes[$((n + 1))]}
# Create missing directories. We use IFS magic to split the path
# into path components.
savedIFS="$IFS"
IFS=/
components=($prefix$target)
fullPath=(.)
for ((m = 0; m < ${#components[*]} - 1; m++)); do
fullPath=("${fullPath[@]}" ${components[m]})
if ! test -d "${fullPath[*]}"; then
mkdir "${fullPath[*]}"
fi
done
IFS="$savedIFS"
ln -sf $source $prefix$target
done
# Create a symlink to the main file.
if ! test "$(readlink $prefix$mainName)" = $main; then
ln -s $main $prefix$mainName
fi
mkdir $out
test "$prefix" && cd $prefix
ls -l
gcc -Wall $cFlags -c $mainName -o $out/$mainName.o