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The log callback runs in the call-home client thread and copied the
matching message into a global buffer, while the test thread polled that
buffer with strlen(), which TSan reported as a data race:
WARNING: ThreadSanitizer: data race (pid=7016)
Read of size 1 at 0x0000019048f0 by thread T2:
#0 server_thread_ssh libnetconf2/tests/test_ch.c:126:15
Previous write of size 8 at 0x0000019048f0 by thread T3:
#0 strncpy
CESNET#1 test_msg_callback libnetconf2/tests/test_ch.c:54:9
CESNET#2 nc_log_vprintf libnetconf2/src/log.c:134:9
CESNET#3 nc_log_printf libnetconf2/src/log.c:152:5
CESNET#4 nc_ch_client_thread libnetconf2/src/session_server.c:4478:17
As if synchronized via sleep:
#0 usleep
CESNET#1 nc_session_free libnetconf2/src/session.c:1206:13
CESNET#2 server_thread_ssh libnetconf2/tests/test_ch.c:122:13
Location is global 'buffer' of size 512 at 0x0000019048f0 (test_ch+0x19048f0)
Thread T2 (tid=7126, running) created by main thread at:
#0 pthread_create
CESNET#1 test_nc_ch_ssh libnetconf2/tests/test_ch.c:249:11
CESNET#2 <null> <null> (libcmocka.so.0+0x618f)
CESNET#3 __libc_start_call_main /usr/src/debug/glibc-2.37-18.fc38.x86_64/csu/../sysdeps/nptl/libc_start_call_main.h:58:16
Thread T3 (tid=7127, running) created by thread T2 at:
#0 pthread_create
CESNET#1 _nc_connect_ch_client_dispatch libnetconf2/src/session_server.c:4770:14
CESNET#2 nc_connect_ch_client_dispatch libnetconf2/src/session_server.c:4813:10
CESNET#3 server_thread_ssh libnetconf2/tests/test_ch.c:113:11
SUMMARY: ThreadSanitizer: data race libnetconf2/tests/test_ch.c:126:15 in server_thread_ssh
The message text itself was never used, so replace the buffer with an
atomic flag.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
The log callback reads the expected message from whichever thread is logging, while the test thread overwrote it with strcpy(). Point to a string literal through an atomic pointer instead. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
michalvasko
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Oct 16, 2026
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Oh, I thought it is just an issue, not a pull request. In any case, I have added a lock for the messages so the error should be gone. |
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We hit this error in the CI: