Created attachment 369809 [details] [review]
patch to fix the issue

Error happens also with 2.56.0 and 2.56.1. Output from gdb:

# random seed: R02S694bbc9f5f0220360e30b12c387ea468
1..25
# Start of websocket tests
# Start of soup tests
[New Thread 0xf6ef7b70 (LWP 62080)]
[New Thread 0xf66f7b70 (LWP 62083)]
# libsoup-DEBUG: stopping input source
# libsoup-DEBUG: closing io stream
# libsoup-DEBUG: stopping input source
# libsoup-DEBUG: closing io stream
[Thread 0xf6ef7b70 (LWP 62080) exited]
ok 1 /websocket/soup/handshake
[New Thread 0xf6ef7b70 (LWP 62084)]
# libsoup-DEBUG: closed: completed io stream close
# libsoup-DEBUG: closed: completed io stream close

Thread 1 "websocket-test" received signal SIGBUS, Bus error.
0xf7f70200 in send_message (self=0x709238, flags=SOUP_WEBSOCKET_QUEUE_NORMAL, 
    opcode=<optimized out>, data=0x18c88 "this is a test", 
    length=<optimized out>)
    at /var/tmp/portage/net-libs/libsoup-2.58.2/work/libsoup-2.58.2/libsoup/
soup-websocket-connection.c:400
400                     * ((guint32 *)mask) = g_random_int ();
(gdb) bt

+ Trace 238481

This is not a bug in the testcase, but in the library itself.