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base repository: NixOS/nixpkgs
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compare: cb007e69a140
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  • 1 commit
  • 2 files changed
  • 1 contributor

Commits on Jan 15, 2020

  1. stdenv: make symlinks that refer to the same output relative 

    While looking at the graph of all the outputs in my personal binary
cache it became obvious that we have a lot of self references within the
package set. That isn't an isuse by itself. However it increases the
size of the binary cache for every (reproducible) build of a package
that carries references to itself. You can no longer deduplicate the
outputs since they are all unique. One of the ways to get rid of (a few)
references is to rewrite all the symlinks that are currently used to be
relative symlinks. Two build of something that didn't really change but
carries a self-reference can the be store as the same NAR file again.

I quickly hacked together this change to see if that would yield and
success. My bash scripting skills are probably not great but so far it
seem to somewhat work.
    @andir @FRidh
    andir authored and FRidh committed Jan 15, 2020

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    tadeokondrak Tadeo Kondrak
    GPG key ID: D41E092CA43F1D8B
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    cb007e6 View commit details
Showing with 29 additions and 0 deletions.
  1. +28 −0 pkgs/build-support/setup-hooks/make-symlinks-relative.sh
  2. +1 −0 pkgs/stdenv/generic/default.nix
28 changes: 28 additions & 0 deletions pkgs/build-support/setup-hooks/make-symlinks-relative.sh
View file
Original file line number Diff line number Diff line change
@@ -0,0 +1,28 @@
fixupOutputHooks+=(_makeSymlinksRelative)

# For every symlink in $output that refers to another file in $output
# ensure that the symlink is relative. This removes references to the output
# has from the resulting store paths and thus the NAR files.
_makeSymlinksRelative() {
local symlinkTarget

if [ -n "${dontRewriteSymlinks-}" ]; then
return 0
fi

while IFS= read -r -d $'\0' f; do
symlinkTarget=$(readlink "$f")
if [[ "$symlinkTarget"/ != "$prefix"/* ]]; then
# skip this symlink as it doesn't point to $prefix
continue
fi

if [ ! -e "$symlinkTarget" ]; then
echo "the symlink $f is broken, it points to $symlinkTarget (which is missing)"
fi

echo "rewriting symlink $f to be relative to $prefix"
ln -snrf "$symlinkTarget" "$f"

done < <(find $prefix -type l -print0)
}
1 change: 1 addition & 0 deletions pkgs/stdenv/generic/default.nix
View file
Original file line number Diff line number Diff line change
@@ -53,6 +53,7 @@ let lib = import ../../../lib; in lib.makeOverridable (
let
defaultNativeBuildInputs = extraNativeBuildInputs ++
[ ../../build-support/setup-hooks/move-docs.sh
../../build-support/setup-hooks/make-symlinks-relative.sh
../../build-support/setup-hooks/compress-man-pages.sh
../../build-support/setup-hooks/strip.sh
../../build-support/setup-hooks/patch-shebangs.sh