From 85147bf69ecd74e05d1c0c65bb2937e4db52340f Mon Sep 17 00:00:00 2001
From: Peter Johnson <johnson.peter@gmail.com>
Date: Thu, 19 Oct 2023 00:14:23 -0700
Subject: [PATCH] [wpinet] WebSocketSerializer: Fix UB (#5787)

---
 .../src/main/native/cpp/WebSocketSerializer.h | 24 ++++++++++++++++---
 1 file changed, 21 insertions(+), 3 deletions(-)

diff --git a/wpinet/src/main/native/cpp/WebSocketSerializer.h b/wpinet/src/main/native/cpp/WebSocketSerializer.h
index 825dfbae26..50c1e0656b 100644
--- a/wpinet/src/main/native/cpp/WebSocketSerializer.h
+++ b/wpinet/src/main/native/cpp/WebSocketSerializer.h
@@ -179,7 +179,13 @@ std::span<const WebSocket::Frame> TrySendFrames(
         bufs.append(it->data.begin(), it->data.end());
       }
       callback(bufs, {});
-      return {&*frameStart, &*frameEnd};
+#ifdef __clang__
+      // work around clang bug
+      return {frames.data() + (frameStart - frames.begin()),
+              frames.data() + (frameEnd - frames.begin())};
+#else
+      return {frameStart, frameEnd};
+#endif
     } else if (sentBytes < 0) {
       // error
       SmallVector<uv::Buffer, 4> bufs;
@@ -208,7 +214,13 @@ std::span<const WebSocket::Frame> TrySendFrames(
           bufs.append(it->data.begin(), it->data.end());
         }
         callback(bufs, {});
-        return {&*frameStart, &*frameEnd};
+#ifdef __clang__
+        // work around clang bug
+        return {frames.data() + (frameStart - frames.begin()),
+                frames.data() + (frameEnd - frames.begin())};
+#else
+        return {frameStart, frameEnd};
+#endif
       }
 
       // build a list of buffers to send as a normal write:
@@ -270,7 +282,13 @@ std::span<const WebSocket::Frame> TrySendFrames(
 
       WS_DEBUG("Write({})\n", writeBufs.size());
       stream.Write(writeBufs, req);
-      return {&*frameStart, &*frameEnd};
+#ifdef __clang__
+      // work around clang bug
+      return {frames.data() + (frameStart - frames.begin()),
+              frames.data() + (frameEnd - frames.begin())};
+#else
+      return {frameStart, frameEnd};
+#endif
     }
   }