Segfault with detached threads and OpenSSL

[Rodrigo Arias]

Hi,

(Sent to cygwin-developers by mistake).

When debugging a segfault in the Dillo browser[1] with the DNS threaded 
resolver and OpenSSL 3.0.13 I managed to isolate a reproducer.

[1]: https://github.com/dillo-browser/dillo/issues/172

It seems to be caused when both the SSL_library_init() is present and the 
PTHREAD_CREATE_DETACHED flag is set.

Steps to reproduce:

$ cat p.c
#include <pthread.h>
#include <unistd.h>
#include <stdio.h>

#include <openssl/ssl.h>

#define N 4

static void *foo(void *data)
{
         printf("hello th %d\n", (int) data);
         return NULL;
}

int main()
{
         SSL_library_init();
         pthread_t th[N];
         pthread_attr_t attr;
         pthread_attr_init(&attr);
         pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);

         for (int i = 0; i < N; i++)
                 pthread_create(&th[i], &attr, foo, (void *) i);

         sleep(5);
}

$ gcc p.c -lssl -pthread -o p

$ gdb ./p
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Reading symbols from ./p...
(gdb) r
Starting program: /home/PC/dillo/build-openssl/p
[New Thread 7332.0x1f2c]
[New Thread 7332.0x99c]
[New Thread 7332.0x27d4]
[New Thread 7332.0x35e0]
[New Thread 7332.0x21dc]
[New Thread 7332.0x3170]
[New Thread 7332.0x1ea4]
[New Thread 7332.0x3180]
hello th 0
hello th 1
hello th 2
[Thread 7332.0x3170 exited with code 0]
hello th 3

Thread 6 "p" received signal SIGSEGV, Segmentation fault.
[Switching to Thread 7332.0x21dc]
0x0000000000000000 in ?? ()

Thanks,
Rodrigo.