On 11/05/2014 12:11 PM, Max Reitz wrote:
>>>> + err->msg = g_strdup_printf("%s: %s", msg1,
>>>> strerror(abs(os_errno)));>> I don't, we really should fix the callers. > > 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 POSIX requires all defined errno values to be positive; negative errno values are unambiguous as values that will cause strerror() to have to generate a message about an unknown value. > (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. This patch is a bandaid; it makes it harder to find callers that need to be fixed. I'd almost argue the exact opposite - add an assert(os_errno > 0). Then we'd loudly break on broken callers, making them easier to find. > > 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. If we're willing to accept the convenience so that callers can be lazy, then I like this patch. If we want to fix bugs in the callers, then this patch makes it harder to find those bugs. I'm actually 60:40 in favor of this patch (I think the convenience outweighs an audit of fixing all callers); but if we do that, then we might also want to intentionally switch existing callers to pass negative values rather than declaring that passing a negative value is a bug. -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
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