Re: [Qemu-devel] [PATCH] error: fixed error_set_errno() to deal with a negative type of os_error.

[Paolo Bonzini <bonzini@gnu.org>]

On 05/11/2014 12:11, Max Reitz wrote:
> 
> Of course I understand, but this patch doesn't make matters worse, as
> long as there are not systems which have negative values for errno
> (which I think we generally assume not to exist throughout qemu). That's
> why I'm fine with it. We should fix the callers but I don't see why we
> shouldn't apply this patch as well.
> 
> A similar issue already came up and led to commit b276d2499, where
> callers of error_setg_errno() assumed that it would not clobber errno,
> so we fixed some of the callers but also applied that commit which just
> saves errno because there's no reason not to.

I think side effect are a different matter than misuse of QEMU.

There are "only" 157 calls to error_setg_errno; 67 use "errno" as the
argument, and 4 use an explicit errno value (one of them is the wrong
-EBUSY).  The other 86 seem correct and should not be hard to audit.

Let's instead add an assertion check to error_setg_errno.

Paolo