fix(FreeBSD): remove null terminator from executable path#14618
Merged
xokdvium merged 1 commit intoNixOS:masterfrom Nov 22, 2025
Merged
fix(FreeBSD): remove null terminator from executable path#14618xokdvium merged 1 commit intoNixOS:masterfrom
xokdvium merged 1 commit intoNixOS:masterfrom
Conversation
On FreeBSD, sysctl(KERN_PROC_PATHNAME) returns a null-terminated
string with pathLen including the terminator. This causes Nix to
fail during manual generation with:
error:
… while calling the 'concatStringsSep' builtin
at /nix/var/nix/builds/nix-63232-402489527/source/doc/manual/generate-settings.nix:99:1:
98| in
99| concatStrings (attrValues (mapAttrs (showSetting prefix) settingsInfo))
| ^
100|
error: input string '/nix/store/gq89cj02b5zs67cbd85vzg5cgsgnd8mj-nix-2.31.2/bin/nix␀'
cannot be represented as Nix string because it contains null bytes
The issue occurs because generate-settings.nix reads the nix binary
path from JSON and evaluates it as a Nix string, which cannot contain
null bytes. Normal C++ string operations don't trigger this since they
handle null-terminated strings correctly.
Strip the null terminator on FreeBSD to match other platforms (Linux
uses /proc/self/exe, macOS uses _NSGetExecutablePath).
Credit: @wahjava (FreeBSD ports and Nixpkgs contributor)
xokdvium
approved these changes
Nov 22, 2025
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
2 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
Motivation
On FreeBSD, sysctl(KERN_PROC_PATHNAME) returns a null-terminated string with pathLen including the terminator. This causes Nix to fail during manual generation with:
The issue occurs because generate-settings.nix reads the nix binary path from JSON and evaluates it as a Nix string, which cannot contain null bytes. Normal C++ string operations don't trigger this since they handle null-terminated strings correctly.
Strip the null terminator on FreeBSD to match other platforms (Linux uses /proc/self/exe, macOS uses _NSGetExecutablePath).
Credit: @wahjava (FreeBSD ports and Nixpkgs contributor)
Context
Building Nix using Nix on FreeBSD (testing native compilation of NixBSD)
This patch comes from freebsd-ports, I tried to improve the explanation and rationale in the comment and commit message. It's helpful to have this change upstream so that it does not need to be patched in manually, and it is relevant for NixBSD.
Add 👍 to pull requests you find important.
The Nix maintainer team uses a GitHub project board to schedule and track reviews.