[musl] insufficient checking in posix_spawn_file_actions_add{open,dup2}

[Bruno Haible <bruno@clisp.org>]

Hi,

POSIX [1][2] says about the functions
  posix_spawn_file_actions_addopen
  posix_spawn_file_actions_adddup2

The function "shall fail if:
  [EBADF]
      The value specified by fildes is negative or greater than or equal to {OPEN_MAX}."

However, in musl libc 1.2.2, these two test programs exit with status 2:
========================================================================
#include <spawn.h>
#include <fcntl.h>
int main ()
{
  posix_spawn_file_actions_t actions;
  if (posix_spawn_file_actions_init (&actions) != 0)
    return 1;
  if (posix_spawn_file_actions_addopen (&actions, 10000000, "foo", 0, O_RDONLY)
      == 0)
    return 2;
  return 0;
}
========================================================================
#include <spawn.h>
int main ()
{
  posix_spawn_file_actions_t actions;
  if (posix_spawn_file_actions_init (&actions) != 0)
    return 1;
  if (posix_spawn_file_actions_adddup2 (&actions, 10000000, 2) == 0)
    return 2;
  return 0;
}
========================================================================

sysconf (_SC_OPEN_MAX) is 1024, on that system.

Best regards,

      Bruno

[1] https://pubs.opengroup.org/onlinepubs/9699919799/functions/posix_spawn_file_actions_addopen.html
[2] https://pubs.opengroup.org/onlinepubs/9699919799/functions/posix_spawn_file_actions_adddup2.html