[Bug libstdc++/67578] New: std::random_device::entropy() always returns 0

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67578

            Bug ID: 67578
           Summary: std::random_device::entropy() always returns 0
           Product: gcc
           Version: 5.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: redi at gcc dot gnu.org
  Target Milestone: ---

When using /dev/random or /dev/urandom on GNU/Linux we can get the bits of
available entropy using the RNDGETENTCNT ioctl.