Ian Jackson writes ("Re: [PATCH v1 3/3] xen-livepatch: If hypervisor is not
compiled with Livepatching"):
> Konrad Rzeszutek Wilk writes ("Re: [PATCH v1 3/3] xen-livepatch: If
> hypervisor is not compiled with Livepatching"):
> > Why would fprintf mess up 'errno' ?
>
> Any libc function is entitled to set errno, if it fails.
And, I forget the exact rules, but I think most are allowed to trash
it even if they succeed. I just remember that errno needs to be saved
across libc calls, if the value is important.
In practice, for example, the first fprintf on a particular FILE* can
end up setting errno to ENOTTY as the libc calls isatty() to decide on
the buffering mode.
Ian.
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