From c61f75388155a8145f20d2bd1bbb7a06e1af65f1 Mon Sep 17 00:00:00 2001
From: Daniel Stenberg <daniel@haxx.se>
Date: Sun, 2 Jun 2024 17:16:58 +0200
Subject: [PATCH] tool_cb_hdr: return error for failed header writes

By checking that fflush() works.

Reported-by: Sebastian Andersson
Fixes #13836
Closes #13859
---
 src/tool_cb_hdr.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/tool_cb_hdr.c b/src/tool_cb_hdr.c
index dab4bb01c1..04c5ba907b 100644
--- a/src/tool_cb_hdr.c
+++ b/src/tool_cb_hdr.c
@@ -105,7 +105,11 @@ size_t tool_header_cb(char *ptr, size_t size, size_t nmemb, void *userdata)
     if(rc != cb)
       return rc;
     /* flush the stream to send off what we got earlier */
-    (void)fflush(heads->stream);
+    if(fflush(heads->stream)) {
+      errorf(per->config->global, "Failed writing headers to %s",
+             per->config->headerfile);
+      return CURL_WRITEFUNC_ERROR;
+    }
   }
 
   curl_easy_getinfo(per->curl, CURLINFO_SCHEME, &scheme);
-- 
2.47.3