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packageOverrides not applied to replaceStdenv's argument. Breaks ccacheStdenv #62121

Piezoid opened this issue May 27, 2019 · 1 comment


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commented May 27, 2019

Issue description

packageOverrides are not (no longer ?) applied in the pkgs argument of replaceStdenv, making the documentation of ccacheStdenv obsolete or unclear.
It seems that an overlay should be used instead. (#43266)

The inline doc in pkgs/top-level/all-packages.nix says:

Wrapper that works as gcc or g++
It can be used by setting in nixpkgs config like this, for example:
   replaceStdenv = { pkgs }: pkgs.ccacheStdenv;
But if you build in chroot, you should have that path in chroot
If instantiated directly, it will use $HOME/.ccache as the cache directory,
i.e. /homeless-shelter/.ccache using the Nix daemon.
You should specify a different directory using an override in
packageOverrides to set extraConfig.

Example using Nix daemon (i.e. multiuser Nix install or on NixOS):
   packageOverrides = pkgs: {
    ccacheWrapper = pkgs.ccacheWrapper.override {
      extraConfig = ''
        export CCACHE_COMPRESS=1
        export CCACHE_DIR=/nix/var/ccache
        export CCACHE_UMASK=007
You can use a different directory, but whichever directory you choose
should be owned by user root, group nixbld with permissions 0770.

Steps to reproduce

However with this config.nix:

    replaceStdenv = { pkgs }: builtins.trace "###Deref ccacheStdenv###" pkgs.ccacheStdenv;
    packageOverrides = pkgs: {
        ccacheWrapper = builtins.trace "###Deref ccacheWrapper###" (pkgs.ccacheWrapper.override {
            extraConfig = builtins.trace "###Deref extraConfig###" ''
                export CCACHE_DIR=/nix/var/ccache
                export CCACHE_UMASK=007

A build like nix-build -A gnum4 ~/repos/nixpkgs --keep-failed fail with:
ccache: error: Failed to create directory /homeless-shelter/.ccache/tmp: Permission denied
indicating that the extraConfig environment variables failled to apply.

Furthermore, only the trace: ###Deref ccacheStdenv### show up. This demonstrate that my overlayed ccacheWrapper is never evaluated.

Using this overlay ~/.config/nixpkgs/overlays/ccacheWrapper.nix worked:

self: super: {
  ccacheWrapper =super.ccacheWrapper.override {
    extraConfig = ''
      export CCACHE_DIR=/nix/var/ccache
      export CCACHE_UMASK=007

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commented Jun 13, 2019

That's indeed a bug and should not exist, however, packageOverrides isn't really maintained anymore either since the way forward is overlays.

Talk about deprecating packageOverrides #43266

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