Why is getentropy marked with warn_unused_result?

[Florian Weimer]

* Paul Pluzhnikov:

> On Sat, Jul 22, 2017 at 2:14 PM, Florian Bruhin <me@the-compiler.org> wrote:
>
>> Why is that, since it shouldn't fail under normal circumstances (at
>> least that's what Qt's sources claim)?
>
> If you didn't check the return value, how would you ever know whether
> you got entropy or not?
>
> The fact that something doesn't fail under normal conditions doesn't
> absolve you from the need to check for abnormal conditions, especially
> when dealing with random data that is likely to be used for crypto.

I did not see the start of the thread.  Was it posted to the
libc-alpha list?  Do you have a pointer to the Qt sources in question?

In practice, a getentropy implementation which does not fail if called
properly requires emulation using /dev/urandom if the system call is
not available in the kernel, but the glibc community rejected that
approach.