← Bilal Elmoussaoui

goblint: A Linter for GObject C Code

· 2 min read · #C · #GObject · #Linting

Over the past week, I’ve been building goblint, a linter specifically designed for GObject-based C codebases.

If you know Rust’s clippy or Go’s go vet, think of goblint as the same thing for GObject/GLib.

Why this exists🔗

A large part of the Linux desktop stack (GTK, Mutter, Pango, NetworkManager) is built on GObject. These projects have evolved over decades and carry a lot of patterns that predate newer GLib helpers, are easy to misuse, or encode subtle lifecycle invariants that nothing verifies.

This leads to issues like missing dispose/finalize/constructed chain-ups (memory leaks or undefined behavior), incorrect property definitions, uninitialized GError* variables, or function declarations with no implementation.

These aren’t theoretical. This GTK merge request recently fixed several missing chain-ups in example code.

Despite this, the C ecosystem lacks a linter that understands GObject semantics. goblint exists to close that gap.

What goblint checks🔗

goblint ships with 35 rules across different categories:

  • Correctness: Real bugs like non-canonical property names, uninitialized GError*, missing PROP_0
  • Suspicious: Likely mistakes like missing implementations or redundant NULL checks
  • Style: Idiomatic GLib usage (g_strcmp0, g_str_equal())
  • Complexity: Suggests modern helpers (g_autoptr, g_clear_*, g_set_str())
  • Performance: Optimizations like G_PARAM_STATIC_STRINGS or g_object_notify_by_pspec()
  • Pedantic: Consistency checks (macro semicolons, matching declare/define pairs)

23 out of 35 rules are auto-fixable. You should apply fixes one rule at a time to review the changes:

goblint --fix --only use_g_strcmp0
goblint --fix --only use_clear_functions

CI/CD Integration🔗

goblint fits into existing pipelines.

GitHub Actions🔗

- name: Run goblint
  run: goblint --format sarif > goblint.sarif

- name: Upload SARIF results
  uses: github/codeql-action/upload-sarif@v3
  with:
    sarif_file: goblint.sarif

Results show up in the Security tab under "Code scanning" and inline on pull requests.

GitLab CI🔗

goblint:
  image: ghcr.io/bilelmoussaoui/goblint:latest
  script:
    - goblint --format sarif > goblint.sarif
  artifacts:
    reports:
      sast: goblint.sarif

Results appear inline in merge requests.

Configuration🔗

Rules default to warn, and can be tuned via goblint.toml:

min_glib_version = "2.40" # Auto-disable rules for newer versions

[rules]
g_param_spec_static_name_canonical = "error" # Make critical
use_g_strcmp0 = "warn" # Keep as warning
use_g_autoptr_inline_cleanup = "ignore" # Disable

# Per-rule ignore patterns
missing_implementation = { level = "error", ignore = ["src/backends/**"] }

You can adopt it gradually without fixing everything at once.

Try it🔗

# Run via container
podman run --rm -v "$PWD:/workspace:Z" ghcr.io/bilelmoussaoui/goblint:latest

# Install locally
cargo install --git https://github.com/bilelmoussaoui/goblint goblint

# Usage
goblint              # Lint current directory
goblint --fix        # Apply automatic fixes
goblint --list-rules # Inspect available rules

The project is early, so feedback is especially valuable (false positives, missing checks, workflow issues, etc.).

Note: The project was originally named "goblin" but was renamed to "goblint" to avoid conflicts with the existing goblin crate for parsing binary formats.