https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100444
Bug ID: 100444
Summary: std::random_device isn't random on AMD
Product: gcc
Version: 10.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: ecree429 at virginmedia dot com
Target Milestone: ---
On certain AMD processors (in my case Ryzen 5 3600, stepping 0, microcode
0x8701013), RDRAND instruction is broken and always returns all-1s. Thus e.g.
#include <iostream>
#include <random>
int main(void)
{
static std::random_device rd;
std::cout << rd() << '\n';
}
always prints 4294967295.
Other RNG implementations such as Qt's QRandomGenerator detect this brokenness
and work around it, falling back to an alternate source of entropy. libstdc++
should ideally do the same, rather than silently failing to be random.
