pkg/afl++: extract runner

pkg/afl++/build.zig

@@ -30,6 +30,30 @@ pub fn addInstrumentedExe(
     return fuzz_exe;
 }
 
+/// Creates a run step that invokes `afl-fuzz` with the given instrumented
+/// executable, input corpus directory, and output directory.
+///
+/// Returns the `Run` step so callers can wire it into a build step.
+pub fn addFuzzerRun(
+    b: *std.Build,
+    exe: std.Build.LazyPath,
+    corpus_dir: std.Build.LazyPath,
+    output_dir: std.Build.LazyPath,
+) *std.Build.Step.Run {
+    const run = b.addSystemCommand(&.{
+        b.findProgram(&.{"afl-fuzz"}, &.{}) catch
+            @panic("Could not find 'afl-fuzz', which is required to run"),
+        "-i",
+    });
+    run.addDirectoryArg(corpus_dir);
+    run.addArgs(&.{"-o"});
+    run.addDirectoryArg(output_dir);
+    run.addArgs(&.{"--"});
+    run.addFileArg(exe);
+    run.addArgs(&.{"@@"});
+    return run;
+}
+
 // Required so `zig build` works although it does nothing.
 pub fn build(b: *std.Build) !void {
     _ = b;

test/fuzz-libghostty/build.zig

@@ -44,20 +44,7 @@ pub fn build(b: *std.Build) void {
     const exe = afl.addInstrumentedExe(b, lib);
 
     // Runner to simplify running afl-fuzz
-    const run = run: {
-        const run = b.addSystemCommand(&.{
-            b.findProgram(&.{"afl-fuzz"}, &.{}) catch
-                @panic("Could not find 'afl-fuzz', which is required to run"),
-            "-i",
-        });
-        run.addDirectoryArg(b.path("corpus/initial"));
-        run.addArgs(&.{"-o"});
-        run.addDirectoryArg(b.path("afl-out"));
-        run.addArgs(&.{"--"});
-        run.addFileArg(exe);
-        run.addArgs(&.{"@@"});
-        break :run run;
-    };
+    const run = afl.addFuzzerRun(b, exe, b.path("corpus/initial"), b.path("afl-out"));
 
     // Install
     b.installArtifact(lib);