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valgrind drd shows potential data race in curl_easy_init

From: Aman Grewal via curl-library <curl-library_at_lists.haxx.se>
Date: Wed, 19 Nov 2025 18:33:58 -0500

Hi all,

I'm running my library under valgrind to try to find any bugs. I'm seeing
this warning stemming from `curl_easy_init` when running drd.

Command: `valgrind --tool=drd --read-var-info=yes --check-stack-var=yes
--free-is-write=yes -s --gen-suppressions=all /test`

Truncated Output:
==8== Thread 3:
==8== Conflicting load by thread 3 at 0x04949724 size 4
==8== at 0x48B8FA2: curl_easy_init (in
/usr/lib/x86_64-linux-gnu/libcurl-gnutls.so.4.8.0)
==8== by 0x40014C1: thread_func (test.c:33)
==8== by 0x485B948: vgDrd_thread_wrapper (drd_pthread_intercepts.c:512)
==8== by 0x49E6AA3: start_thread (pthread_create.c:447)
==8== by 0x4A73A63: clone (clone.S:100)
==8== Allocation context: BSS section of
/usr/lib/x86_64-linux-gnu/libcurl-gnutls.so.4.8.0
==8== Other segment start (thread 2)
==8== at 0x4A73A56: clone (clone.S:83)
==8== by 0x49E671F: ??? (allocatestack.c:605)
==8== by 0x67036BF: ???
==8== Other segment end (thread 2)
==8== at 0x4A759DB: connect (connect.c:26)
==8== by 0x48A7DEC: ??? (in
/usr/lib/x86_64-linux-gnu/libcurl-gnutls.so.4.8.0)
==8== by 0x48B42E7: ??? (in
/usr/lib/x86_64-linux-gnu/libcurl-gnutls.so.4.8.0)
==8== by 0x48B517F: ??? (in
/usr/lib/x86_64-linux-gnu/libcurl-gnutls.so.4.8.0)
==8== by 0x48A8FC5: ??? (in
/usr/lib/x86_64-linux-gnu/libcurl-gnutls.so.4.8.0)
==8== by 0x48EAED7: ??? (in
/usr/lib/x86_64-linux-gnu/libcurl-gnutls.so.4.8.0)
==8== by 0x48ED5D9: curl_multi_perform (in
/usr/lib/x86_64-linux-gnu/libcurl-gnutls.so.4.8.0)
==8== by 0x48BBE3A: curl_easy_perform (in
/usr/lib/x86_64-linux-gnu/libcurl-gnutls.so.4.8.0)
==8== by 0x4001553: thread_func (test.c:38)
==8== by 0x485B948: vgDrd_thread_wrapper (drd_pthread_intercepts.c:512)
==8== by 0x49E6AA3: start_thread (pthread_create.c:447)
==8== by 0x4A73A63: clone (clone.S:100)
==8==

When I run the same valgrind command on the sample code in
https://curl.se/libcurl/c/threaded-ssl.html, I see similar warnings, so I'm
hoping this is a spurious warning. Has anyone seen this before? Is it safe
to add it to my suppressions file?


I'm running this on Ubuntu 24.04 (LTS), and I'm using the libcurl3t64-gnutls
package.



Thanks,
Aman Grewal 


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Received on 2025-11-20