add fuzzer

meson.build

@@ -1,6 +1,6 @@
 project(
     'gentoo-utils',
-    'rust',
+    ['rust', 'cpp'],
     meson_version: '>=1.9.1',
     default_options: {'rust_std': '2024', 'rust_nightly': 'enabled'},
 )
@@ -16,5 +16,7 @@ gentoo_utils = static_library(
     'gentoo_utils',
     'src/lib.rs',
     dependencies: [mon, get, itertools],
-    link_with: [thiserror]
+    link_with: [thiserror],
 )
+
+subdir('tests')

meson.options

@@ -0,0 +1 @@
+option('fuzz', type: 'feature', value: 'disabled')

scripts/atom.py

@@ -0,0 +1,13 @@
+#!/usr/bin/env python3
+
+import sys
+import portage.dep as dep
+
+input = sys.stdin.read().strip()
+
+try:
+    dep.Atom(input)
+except Exception as e:
+    sys.exit(1)
+
+sys.exit(0)

tests/fuzz.rs

@@ -0,0 +1,50 @@
+use core::slice;
+use gentoo_utils::{Parseable, atom::Atom};
+use mon::{Parser, ParserFinishedError, input::InputIter};
+use std::{
+    io::Write,
+    process::{Command, Stdio},
+};
+
+#[allow(clippy::missing_safety_doc, clippy::needless_return)]
+#[unsafe(no_mangle)]
+pub unsafe extern "C" fn LLVMFuzzerTestOneInput(input: *const u8, len: usize) -> i32 {
+    let slice = unsafe { slice::from_raw_parts(input, len) };
+
+    let atom = match str::from_utf8(slice) {
+        Ok(str) => str.trim(),
+        _ => return -1,
+    };
+
+    let mut proc = Command::new("atom.py")
+        .stdin(Stdio::piped())
+        .spawn()
+        .unwrap();
+
+    proc.stdin
+        .as_mut()
+        .unwrap()
+        .write_all(atom.as_bytes())
+        .unwrap();
+
+    let status = proc.wait().unwrap();
+
+    let result = Atom::parser().check_finished(InputIter::new(atom));
+
+    match (status.success(), result) {
+        (true, Ok(_)) => {
+            eprintln!("agreement that {atom} is valid");
+            return 0;
+        }
+        (true, Err(ParserFinishedError::Err(it) | ParserFinishedError::Unfinished(it))) => {
+            panic!("gentoo-utils rejected valid atom: {atom}: {}", it.rest());
+        }
+        (false, Err(_)) => {
+            eprintln!("agreement that {atom} is invalid");
+            return -1;
+        }
+        (false, Ok(_)) => {
+            panic!("gentoo-utils accepted invalid atom: {atom}");
+        }
+    }
+}

tests/meson.build

@@ -0,0 +1,27 @@
+cbindgen = find_program('cbindgen')
+
+fuzz_h = custom_target(
+    'fuzz_h',
+    input: 'fuzz.rs',
+    output: 'fuzz.h',
+    command: [cbindgen, '@INPUT@', '-o', '@OUTPUT'],
+)
+
+fuzz_rs = static_library(
+    'fuzz_rs',
+    'fuzz.rs',
+    rust_abi: 'c',
+    rust_args: [
+        '-Cpasses=sancov-module',
+        '-Cllvm-args=-sanitizer-coverage-level=3',
+        '-Cllvm-args=-sanitizer-coverage-inline-8bit-counters',
+    ],
+    dependencies: [mon],
+    link_with: [gentoo_utils],
+)
+
+fuzz_cpp = executable(
+    'fuzz',
+    link_args: ['-fsanitize=fuzzer'],
+    link_with: [fuzz_rs],
+)