From c3a417206a6780393dae871a351fb9617012aee2 Mon Sep 17 00:00:00 2001
From: Kendall Condon <goon.pri.low@gmail.com>
Date: Wed, 11 Mar 2026 20:23:23 -0400
Subject: [PATCH] libfuzzer: check weights for bytes mutations

---
 lib/fuzzer.zig | 22 ++++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)

diff --git a/lib/fuzzer.zig b/lib/fuzzer.zig
index c97aeea4e8..d900bed11e 100644
--- a/lib/fuzzer.zig
+++ b/lib/fuzzer.zig
@@ -1320,13 +1320,23 @@ const Fuzzer = struct {
 
         if (opts.copy != 0) {
             if (opts.fresh == 0 or slice_i == data_slice.len) return .fresh;
-            return .{ .mutate = switch (uid.kind) {
-                .int => .{ .int = data.ints[data_i] },
-                .bytes => .{ .bytes = b: {
+            switch (uid.kind) {
+                .int => {
+                    const int = data.ints[data_i];
+                    if (weightsContain(int, weights)) {
+                        @branchHint(.likely);
+                        return .{ .mutate = .{ .int = int } };
+                    }
+                },
+                .bytes => {
                     const entry = data.bytes.entries[data_i];
-                    break :b data.bytes.table[entry.off..][0..entry.len];
-                } },
-            } };
+                    const bytes = data.bytes.table[entry.off..][0..entry.len];
+                    if (weightsContainBytes(bytes, weights)) {
+                        @branchHint(.likely);
+                        return .{ .mutate = .{ .bytes = bytes } };
+                    }
+                },
+            }
         }
 
         if (!opts.splice) {