fix OOB in pathToFileURL with long relative paths

src/resolver/resolve_path.zig

@@ -2048,13 +2048,18 @@ export fn ResolvePath__joinAbsStringBufCurrentPlatformBunString(
     const str = in.toUTF8WithoutRef(bun.default_allocator);
     defer str.deinit();
 
-    const out_slice = joinAbsStringBuf(
-        globalObject.bunVM().transpiler.fs.top_level_dir,
-        &join_buf,
-        &.{str.slice()},
-        .auto,
-    );
+    const cwd = globalObject.bunVM().transpiler.fs.top_level_dir;
+    const input = str.slice();
+    const total = cwd.len + input.len + 2;
+
+    if (total <= join_buf.len) {
+        const out_slice = joinAbsStringBuf(cwd, &join_buf, &.{input}, .auto);
+        return bun.String.cloneUTF8(out_slice);
+    }
 
+    const buf = bun.handleOom(bun.default_allocator.alloc(u8, total));
+    defer bun.default_allocator.free(buf);
+    const out_slice = joinAbsStringBuf(cwd, buf, &.{input}, .auto);
     return bun.String.cloneUTF8(out_slice);
 }
 

test/js/node/url/pathToFileURL.test.ts

@@ -5,6 +5,13 @@ test("pathToFileURL doesn't leak memory", () => {
   expect([path.join(import.meta.dir, "pathToFileURL-leak-fixture.js")]).toRun();
 });
 
+test("pathToFileURL handles relative paths longer than 4096 bytes", () => {
+  expect([
+    "-e",
+    'const p = Buffer.alloc(200000, "a").toString(); const u = Bun.pathToFileURL(p); if (!u.href.endsWith("/" + p)) throw new Error(u.href)',
+  ]).toRun();
+});
+
 test("pathToFileURL escapes special characters", () => {
   const cases = [
     ["\0", "%00"], // '\0' == 0x00