Zero Hydra Failures towards 23.11 NixOS release

November 8, 2023


The next NixOS-23.11 will be released around the end of November. Current development phase is called Zero Hydra Failures (ZHF): at this time the main focus is to fix as many build failures in nixpkgs/master repository as possible before the final release.

Issue #265948 (and the discourse topic) is the tracker where you can get hints on how to help fixing known broken packages and review already proposed fixes.

It is a great time to contribute to nixpkgs!

To follow the tradition let’s fix one package here.

newlib example

trunk jobset shows us about ~3800 build failure. I picked newlib failure and will try to fix it. The install part fails there as:

install flags: SHELL=/nix/store/lf0wpjrj8yx4gsmw2s3xfl58ixmqk8qa-bash-5.2-p15/bin/bash install
make[1]: Entering directory '/build/newlib-'
/nix/store/lf0wpjrj8yx4gsmw2s3xfl58ixmqk8qa-bash-5.2-p15/bin/bash ./mkinstalldirs /nix/store/1wxhiz8jkyff6chkwp89vy85qlgvi7ij-newlib- /nix/store/1wxhiz8jkyff6chkwp89vy85qlgvi7ij-newlib-
make[2]: Entering directory '/build/newlib-'
make[3]: Entering directory '/build/newlib-'
make[3]: Nothing to be done for 'install-exec-am'.
make[3]: Nothing to be done for 'install-data-am'.
make[3]: Leaving directory '/build/newlib-'
make[2]: Leaving directory '/build/newlib-'
make[1]: Nothing to be done for 'install-target'.
make[1]: Leaving directory '/build/newlib-'
$out is empty

I have no idea why the build fails. Let’s find out the hard way.

The build tab tells us that last successful build of newlib was around 2023-06-18 on d9895270b775226e0fdabd7937af2d236abe4eb2 nixpkgs input. And first failed commit was 8277b539d371bf4308fc5097911aa58bfac1794f around 2023-07-01.

Running bisect:

$ git bisect start 8277b539d371bf4308fc5097911aa58bfac1794f d9895270b775226e0fdabd7937af2d236abe4eb2
$ git bisect run nix build -f. newlib

commit cf1b7c4d5c027837e71d284a838fbeb05b3fcb7f
Date:   Sat Jun 24 01:13:17 2023 +0200

    newlib: fix build of nano variant on non-ARM architectures

The full diff of this commit is small an readable:

--- a/pkgs/development/misc/newlib/default.nix
+++ b/pkgs/development/misc/newlib/default.nix
@@ -73,10 +73,12 @@ stdenv.mkDerivation (finalAttrs: {
       cd $out${finalAttrs.passthru.libdir}

       for f in librdimon.a libc.a libg.a; do
-        cp "$f" "''${f%%\.a}_nano.a"
+        # Some libraries are only available for specific architectures.
+        # For example, librdimon.a is only available on ARM.
+        [ -f "$f" ] && cp "$f" "''${f%%\.a}_nano.a"
-  '';
+  '' + ''[ "$(find $out -type f | wc -l)" -gt 0 ] || (echo '$out is empty' 1>&2 && exit 1)'';

   passthru = {
     incdir = "/${stdenv.targetPlatform.config}/include";

In our case of newlib (not newlib-nano) the only change is the addition of [ "$(find $out -type f | wc -l)" -gt 0 ] || (echo '$out is empty' 1>&2 && exit 1) line. It causes build to fail if $out is empty. The $out was always empty for newlib.x86_64-linux. Normally the newlib output contains something only for bare-metal targets like pkgsCross.x86_64-embedded.newlib.

Thus the fix is to constrain newlib to only those targets:

--- a/pkgs/development/misc/newlib/default.nix
+++ b/pkgs/development/misc/newlib/default.nix
@@ -96,5 +96,9 @@ stdenv.mkDerivation (finalAttrs: {
     # COPYING3
     license = licenses.gpl2Plus;
+    # newlib frequently does ont supply any files on hosted targets like
+    # x86_64-unknown-linux-gnu:
+    # Let's constrain `newlib` package to bare-metal alone.
+    broken = !stdenv.hostPlatform.isNone;

This change was proposed as PR #266268.

Parting words

Fixing package breakages are usually easier if the package used to work at some point before. Otherwise we can always mark packages broken and schedule them for removal.

Have fun!