On linux, the assumption that file descriptors 0 - 2 belong to stdio
is not correct. They do by default, but they can be closed by the shell at
program launch.

For example, it is possible for someone to use 2>&- on the program command
line, which closes STDERR when running.

This can trigger an abort in libuv due to the assertion fd > STDERR_FILENO in
uv__close.

This can be readily reproduced using the helloworld/main.c example at
#https://docs.libuv.org/en/v1.x/guide/basics.html

#include <stdio.h>
#include <stdlib.h>
#include <uv.h>

int main() {

    uv_loop_t *loop = malloc(sizeof(uv_loop_t));
    uv_loop_init(loop);

    printf("Now quitting.\n");
    uv_run(loop, UV_RUN_DEFAULT);

    uv_loop_close(loop);
    free(loop);
    return 0;

}

The issue occurs because closing STDERR will make file descriptor 2 the
next lowest available file descriptor, which will be consumed by epoll_create1()
in the call trace

uv_loop_init
-> uv__platform_loop_init
-> epoll_create1

Since 2 i now the next lowest unused file descriptor, epoll_create1 will
return 2.

Then,

uv_loop_close
-> uv__close

will fail the assert in uv__close when this file descriptor is passed

There may be other paths for which this can occur, but this appears
to likely be the most common.