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/* This testcase is part of GDB, the GNU debugger.
Copyright 2009-2022 Free Software Foundation, Inc.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
The original issue we're trying to test is described in this
thread:
https://sourceware.org/legacy-ml/gdb-patches/2009-06/msg00802.html
The NEW_THREAD_EVENT code the comments below refer to no longer
exists in GDB, so the following comments are kept for historical
reasons, and to guide future updates to the testcase.
---
Do not use threads as we need to exploit a bug in LWP code masked by the
threads code otherwise.
INFERIOR_PTID must point to exited LWP. Here we use the initial LWP as it
is automatically INFERIOR_PTID for GDB.
Finally we need to call target_resume (RESUME_ALL, ...) which we invoke by
NEW_THREAD_EVENT (called from the new LWP as initial LWP is exited now). */
#define _GNU_SOURCE
#include <sched.h>
#include <assert.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/wait.h>
#define STACK_SIZE 0x1000
/* True if the 'fn_return' thread has been reached at the point after
its parent is already gone. */
volatile int fn_return_reached = 0;
/* True if the 'fn' thread has exited. */
volatile int fn_exited = 0;
/* Wrapper around clone. */
static int
do_clone (int (*fn)(void *))
{
unsigned char *stack;
int new_pid;
stack = malloc (STACK_SIZE);
assert (stack != NULL);
new_pid = clone (fn, stack + STACK_SIZE, CLONE_FILES | CLONE_VM,
NULL, NULL, NULL, NULL);
assert (new_pid > 0);
return new_pid;
}
static int
fn_return (void *unused)
{
/* Wait until our direct parent exits. We want the breakpoint set a
couple lines below to hit with the previously-selected thread
gone. */
while (!fn_exited)
usleep (1);
fn_return_reached = 1; /* at-fn_return */
return 0;
}
static int
fn (void *unused)
{
do_clone (fn_return);
return 0;
}
int
main (int argc, char **argv)
{
int new_pid, status, ret;
new_pid = do_clone (fn);
/* Note the clone call above didn't use CLONE_THREAD, so it actually
put the new child in a new thread group. However, the new clone
is still reported with PTRACE_EVENT_CLONE to GDB, since we didn't
use CLONE_VFORK (results in PTRACE_EVENT_VFORK) nor set the
termination signal to SIGCHLD (results in PTRACE_EVENT_FORK), so
GDB thinks of it as a new thread of the same inferior. It's a
bit of an odd setup, but it's not important for what we're
testing, and, it let's us conveniently use waitpid to wait for
the child, which you can't with CLONE_THREAD. */
ret = waitpid (new_pid, &status, __WALL);
assert (ret == new_pid);
assert (WIFEXITED (status) && WEXITSTATUS (status) == 0);
fn_exited = 1;
/* Don't exit before the breakpoint at fn_return triggers. */
while (!fn_return_reached)
usleep (1);
return 0;
}
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