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From: Michael Tokarev <mjt@tls.msk.ru>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: qemu-trivial@nongnu.org, qemu-devel@nongnu.org
Subject: Re: [Qemu-trivial] [Qemu-devel] [PATCH] vnc: fix "info vnc" with "-vnc ..., reverse=on"
Date: Tue, 16 Oct 2012 10:33:23 +0400	[thread overview]
Message-ID: <507CFFB3.7070907@msgid.tls.msk.ru> (raw)
In-Reply-To: <1349872258-21952-1-git-send-email-pbonzini@redhat.com>

On 10.10.2012 16:30, Paolo Bonzini wrote:
[]
> --- a/ui/vnc.c
> +++ b/ui/vnc.c
> @@ -372,6 +372,10 @@ VncInfo *qmp_query_vnc(Error **errp)
>              }
>          }
>  
> +        if (vnc_display->lsock == -1) {

FWIW, can't we use "< 0" condition in all cases like this - for
testing whenever a filedescriptor is not open or if a system call
returned failure?  Why we compare with -1 only?  The "< 0" comparison
is cheaper in the resulting code (very very small difference), but
more to the point, it guarantees that no invalid value is treated
as valid - for example, in case some function returns -errno like
it was with bdrv_something() recently.  I use "< 0" in such places
for over 20 years for this reason, this "technique" saved me
countless number of times, when old API changed, or when I switched
to a new API without reviewing return value checking in all places,
or when I just didn't read the manpage carefully... ;)

Thanks,

/mjt


WARNING: multiple messages have this Message-ID (diff)
From: Michael Tokarev <mjt@tls.msk.ru>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: qemu-trivial@nongnu.org, qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [PATCH] vnc: fix "info vnc" with "-vnc ..., reverse=on"
Date: Tue, 16 Oct 2012 10:33:23 +0400	[thread overview]
Message-ID: <507CFFB3.7070907@msgid.tls.msk.ru> (raw)
In-Reply-To: <1349872258-21952-1-git-send-email-pbonzini@redhat.com>

On 10.10.2012 16:30, Paolo Bonzini wrote:
[]
> --- a/ui/vnc.c
> +++ b/ui/vnc.c
> @@ -372,6 +372,10 @@ VncInfo *qmp_query_vnc(Error **errp)
>              }
>          }
>  
> +        if (vnc_display->lsock == -1) {

FWIW, can't we use "< 0" condition in all cases like this - for
testing whenever a filedescriptor is not open or if a system call
returned failure?  Why we compare with -1 only?  The "< 0" comparison
is cheaper in the resulting code (very very small difference), but
more to the point, it guarantees that no invalid value is treated
as valid - for example, in case some function returns -errno like
it was with bdrv_something() recently.  I use "< 0" in such places
for over 20 years for this reason, this "technique" saved me
countless number of times, when old API changed, or when I switched
to a new API without reviewing return value checking in all places,
or when I just didn't read the manpage carefully... ;)

Thanks,

/mjt

  parent reply	other threads:[~2012-10-16  6:33 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-10-10 12:30 [Qemu-trivial] [PATCH] vnc: fix "info vnc" with "-vnc ..., reverse=on" Paolo Bonzini
2012-10-10 12:30 ` [Qemu-devel] " Paolo Bonzini
2012-10-12  8:55 ` [Qemu-trivial] " Stefan Hajnoczi
2012-10-12  8:55   ` [Qemu-devel] " Stefan Hajnoczi
2012-10-16  6:33 ` Michael Tokarev [this message]
2012-10-16  6:33   ` [Qemu-devel] " Michael Tokarev

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