From a09aaf06ecd52ed4c2d623dc9a617d9411a1f3c3 Mon Sep 17 00:00:00 2001
From: Hannah Shi <hannahshisfb@gmail.com>
Date: Thu, 15 Aug 2024 09:16:58 -0700
Subject: [PATCH] [ObjC] fix error handling in CFWriteStreamWrite (#37344)

follow up of #37255

Closes #37344

COPYBARA_INTEGRATE_REVIEW=https://github.com/grpc/grpc/pull/37344 from HannahShiSFB:cfstream-write-error-handling c9a751d9d73debb53c1d2f8b81808ca874e76836
PiperOrigin-RevId: 663329438
---
 .../lib/event_engine/cf_engine/cfstream_endpoint.cc   | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/src/core/lib/event_engine/cf_engine/cfstream_endpoint.cc b/src/core/lib/event_engine/cf_engine/cfstream_endpoint.cc
index 47e67d8e4a48f..4721437860b91 100644
--- a/src/core/lib/event_engine/cf_engine/cfstream_endpoint.cc
+++ b/src/core/lib/event_engine/cf_engine/cfstream_endpoint.cc
@@ -335,9 +335,18 @@ void CFStreamEndpointImpl::DoWrite(
       continue;
     }
 
-    size_t written_size =
+    CFIndex written_size =
         CFWriteStreamWrite(cf_write_stream_, slice.begin(), slice.size());
 
+    if (written_size < 0) {
+      auto status = CFErrorToStatus(CFWriteStreamCopyError(cf_write_stream_));
+      GRPC_TRACE_LOG(event_engine_endpoint, INFO)
+          << "CFStream write error: " << status
+          << ", written_size: " << written_size;
+      on_writable(status);
+      return;
+    }
+
     total_written_size += written_size;
     if (written_size < slice.size()) {
       SliceBuffer written;