fix: patch libfuzzer to support jobs argument

lib/bolero-libfuzzer/bolero-fixes.patch

@@ -0,0 +1,48 @@
+diff -ruN libfuzzer/FuzzerCommand.h b/libfuzzer/FuzzerCommand.h
+index f653fe3..678573e 100644
+--- libfuzzer/FuzzerCommand.h
++++ b/libfuzzer/FuzzerCommand.h
+@@ -139,16 +139,35 @@ public:
+   // be the equivalent command line.
+   std::string toString() const {
+     std::stringstream SS;
+-    for (auto arg : getArguments())
+-      SS << arg << " ";
++    auto test_name = std::getenv("BOLERO_TEST_NAME");
++    auto libtest_harness = std::getenv("BOLERO_LIBTEST_HARNESS");
++    auto args = getArguments();
++
++    SS << "env";
++
++    if (libtest_harness) {
++      SS << " BOLERO_LIBTEST_HARNESS=1 BOLERO_TEST_NAME=\"" << test_name << "\"";
++    }
++
++    SS << " BOLERO_LIBFUZZER_ARGS=\"";
++    if (args.size() > 1)
++      SS << args[1];
++    for (unsigned i = 2; i < args.size(); ++i)
++      SS << " " << args[i];
++    SS << "\"";
++
++    SS << " " << args[0];
++
++    if (libtest_harness) {
++      SS << " " << test_name << " --exact --nocapture --quiet --test-threads 1";
++    }
++
+     if (hasOutputFile())
+-      SS << ">" << getOutputFile() << " ";
++      SS << " >" << getOutputFile();
+     if (isOutAndErrCombined())
+-      SS << "2>&1 ";
+-    std::string result = SS.str();
+-    if (!result.empty())
+-      result = result.substr(0, result.length() - 1);
+-    return result;
++      SS << " 2>&1";
++
++    return SS.str();
+   }
+
+ private:

lib/bolero-libfuzzer/build.rs

@@ -3,6 +3,7 @@ extern crate cc;
 fn main() {
     println!("cargo:rerun-if-env-changed=BOLERO_FUZZER");
     println!("cargo:rerun-if-env-changed=CARGO_CFG_FUZZING_LIBFUZZER");
+    println!("cargo:rerun-if-changed=libfuzzer/");
 
     if std::env::var("CARGO_CFG_FUZZING_LIBFUZZER").is_ok() {
         let mut build = cc::Build::new();

lib/bolero-libfuzzer/libfuzzer/FuzzerCommand.h

@@ -139,16 +139,35 @@ class Command final {
   // be the equivalent command line.
   std::string toString() const {
     std::stringstream SS;
-    for (auto arg : getArguments())
-      SS << arg << " ";
+    auto test_name = std::getenv("BOLERO_TEST_NAME");
+    auto libtest_harness = std::getenv("BOLERO_LIBTEST_HARNESS");
+    auto args = getArguments();
+
+    SS << "env";
+
+    if (libtest_harness) {
+      SS << " BOLERO_LIBTEST_HARNESS=1 BOLERO_TEST_NAME=\"" << test_name << "\"";
+    }
+
+    SS << " BOLERO_LIBFUZZER_ARGS=\"";
+    if (args.size() > 1)
+      SS << args[1];
+    for (unsigned i = 2; i < args.size(); ++i)
+      SS << " " << args[i];
+    SS << "\"";
+
+    SS << " " << args[0];
+
+    if (libtest_harness) {
+      SS << " " << test_name << " --exact --nocapture --quiet --test-threads 1";
+    }
+
     if (hasOutputFile())
-      SS << ">" << getOutputFile() << " ";
+      SS << " >" << getOutputFile();
     if (isOutAndErrCombined())
-      SS << "2>&1 ";
-    std::string result = SS.str();
-    if (!result.empty())
-      result = result.substr(0, result.length() - 1);
-    return result;
+      SS << " 2>&1";
+
+    return SS.str();
   }
 
 private:

lib/bolero-libfuzzer/src/lib.rs

@@ -93,12 +93,23 @@ pub mod fuzzer {
             ));
         }
 
-        if std::env::var("__BOLERO_LIBFUZZER_RECURSE").is_ok() {
+        // Libfuzzer can generate multiple jobs that can make the binary recurse.
+        // Still, let’s limit recursion depth to some reasonable amount.
+        let recursion_level = std::env::var("__BOLERO_LIBFUZZER_RECURSE")
+            .as_deref()
+            .unwrap_or("0")
+            .parse()
+            .unwrap_or(usize::MAX);
+
+        if recursion_level > 10 {
             eprintln!("LOOPING BINARY");
             std::process::exit(1);
         }
 
-        std::env::set_var("__BOLERO_LIBFUZZER_RECURSE", "1");
+        std::env::set_var(
+            "__BOLERO_LIBFUZZER_RECURSE",
+            (recursion_level + 1).to_string(),
+        );
 
         // create a vector of NULL terminated strings
         let args = std::env::args()

lib/bolero-libfuzzer/update.sh

@@ -10,3 +10,4 @@ git clone --depth 1 --single-branch --branch $version https://github.com/llvm/ll
 rm -rf "$project_dir/libfuzzer/"
 mv "$tmp_dir/compiler-rt/lib/fuzzer/" "$project_dir/libfuzzer"
 mv "$tmp_dir/compiler-rt/LICENSE.TXT" "$project_dir/libfuzzer/LICENSE.TXT"
+patch -p0 < bolero-fixes.patch

tests/src/engines.rs

@@ -21,18 +21,30 @@ pub fn test() -> Result {
             supports_env: engine != "kani",
             test_crashes: engine != "afl", // TODO fix this
             runs: 10_000,
+            jobs: None,
         };
 
         test.run()?;
 
-        if ["libfuzzer", "hongfuzz"].contains(&engine) {
+        if ["libfuzzer", "honggfuzz"].contains(&engine) {
             Test {
                 sanitizer: "address".to_string(),
                 rustc_bootstrap: !is_nightly,
                 ..test.clone()
             }
             .run()?;
         }
+
+        // libfuzzer supports multiple jobs
+        if ["libfuzzer"].contains(&engine) {
+            Test {
+                sanitizer: "address".to_string(),
+                rustc_bootstrap: !is_nightly,
+                jobs: Some(2),
+                ..test.clone()
+            }
+            .run()?;
+        }
     }
 
     Ok(())
@@ -48,6 +60,7 @@ struct Test {
     supports_env: bool,
     test_crashes: bool,
     runs: u32,
+    jobs: Option<u32>,
 }
 
 impl Test {
@@ -77,6 +90,12 @@ impl Test {
             args.push("--rustc-bootstrap".to_string());
         }
 
+        let jobs = &if let Some(jobs) = self.jobs {
+            vec!["--jobs".to_string(), jobs.to_string()]
+        } else {
+            vec![]
+        };
+
         let args = &args;
 
         for test in [
@@ -92,7 +111,11 @@ impl Test {
                 continue;
             }
 
-            cmd!(sh, "{cargo_bolero} test {test} --runs {runs} {args...}").run()?;
+            cmd!(
+                sh,
+                "{cargo_bolero} test {test} --runs {runs} {jobs...} {args...}"
+            )
+            .run()?;
 
             if self.reduce {
                 cmd!(sh, "{cargo_bolero} reduce {test} {args...}").run()?;
@@ -117,7 +140,7 @@ impl Test {
                 let _ = sh.remove_path(format!("src/__fuzz__/{test}"));
             }
 
-            let res = cmd!(sh, "{cargo_bolero} test {test} {args...}").run();
+            let res = cmd!(sh, "{cargo_bolero} test {test} {args...} {jobs...}").run();
 
             assert!(res.is_err(), "test {test} should catch a panic");
         }