[Qemu-devel] [PATCH] block/vvfat.c: remove debugging code to reinit stderr if NULL

[Qemu-devel] [PATCH] block/vvfat.c: remove debugging code to reinit stderr if NULL

[Michael Tokarev]

Just log to stderr unconditionally, like other similar code does.

Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
---
 block/vvfat.c |    5 -----
 1 file changed, 5 deletions(-)

diff --git a/block/vvfat.c b/block/vvfat.c
index 70176b1..ea37023 100644
--- a/block/vvfat.c
+++ b/block/vvfat.c
@@ -1082,11 +1082,6 @@ static int vvfat_open(BlockDriverState *bs, QDict *options, int flags,
     vvv = s;
 #endif
 
-DLOG(if (stderr == NULL) {
-    stderr = fopen("vvfat.log", "a");
-    setbuf(stderr, NULL);
-})
-
     opts = qemu_opts_create(&runtime_opts, NULL, 0, &error_abort);
     qemu_opts_absorb_qdict(opts, options, &local_err);
     if (local_err) {
-- 
1.7.10.4

Re: [Qemu-devel] [PATCH] block/vvfat.c: remove debugging code to reinit stderr if NULL

[Peter Maydell]

On 18 August 2014 12:41, Michael Tokarev <mjt@tls.msk.ru> wrote:
> Just log to stderr unconditionally, like other similar code does.
>
> Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
> ---
>  block/vvfat.c |    5 -----
>  1 file changed, 5 deletions(-)
>
> diff --git a/block/vvfat.c b/block/vvfat.c
> index 70176b1..ea37023 100644
> --- a/block/vvfat.c
> +++ b/block/vvfat.c
> @@ -1082,11 +1082,6 @@ static int vvfat_open(BlockDriverState *bs, QDict *options, int flags,
>      vvv = s;
>  #endif
>
> -DLOG(if (stderr == NULL) {
> -    stderr = fopen("vvfat.log", "a");
> -    setbuf(stderr, NULL);
> -})
> -
>      opts = qemu_opts_create(&runtime_opts, NULL, 0, &error_abort);
>      qemu_opts_absorb_qdict(opts, options, &local_err);
>      if (local_err) {
> --
> 1.7.10.4

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>

thanks
-- PMM

Re: [Qemu-devel] [PATCH] block/vvfat.c: remove debugging code to reinit stderr if NULL

[Kevin Wolf]

Am 18.08.2014 um 13:41 hat Michael Tokarev geschrieben:
> Just log to stderr unconditionally, like other similar code does.
> 
> Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
> ---
>  block/vvfat.c |    5 -----
>  1 file changed, 5 deletions(-)
> 
> diff --git a/block/vvfat.c b/block/vvfat.c
> index 70176b1..ea37023 100644
> --- a/block/vvfat.c
> +++ b/block/vvfat.c
> @@ -1082,11 +1082,6 @@ static int vvfat_open(BlockDriverState *bs, QDict *options, int flags,
>      vvv = s;
>  #endif
>  
> -DLOG(if (stderr == NULL) {
> -    stderr = fopen("vvfat.log", "a");
> -    setbuf(stderr, NULL);
> -})
> -
>      opts = qemu_opts_create(&runtime_opts, NULL, 0, &error_abort);
>      qemu_opts_absorb_qdict(opts, options, &local_err);
>      if (local_err) {

Michael, it's fine to merge trivial block patches through your tree, but
can you please keep Stefan and me CCed anyway?

This specific patch isn't as trivial as it might look at the first
sight (in other words: it's wrong). The part that you probably missed is
that stderr isn't the real one when DEBUG is set:

    #undef stderr
    #define stderr STDERR
    FILE* stderr = NULL;

So now you have a lot of fprintf(NULL, ...), which obviously makes qemu
segfault as soon as you enable debugging for vvfat.

Kevin

Re: [Qemu-devel] [PATCH] block/vvfat.c: remove debugging code to reinit stderr if NULL

[Peter Maydell]

On 19 August 2014 12:58, Kevin Wolf <kwolf@redhat.com> wrote:
> This specific patch isn't as trivial as it might look at the first
> sight (in other words: it's wrong). The part that you probably missed is
> that stderr isn't the real one when DEBUG is set:
>
>     #undef stderr
>     #define stderr STDERR
>     FILE* stderr = NULL;

Yikes. Can we rip that out as well, then?

-- PMM

Re: [Qemu-devel] [PATCH] block/vvfat.c: remove debugging code to reinit stderr if NULL

[Eric Blake]

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On 08/19/2014 05:58 AM, Kevin Wolf wrote:
> Am 18.08.2014 um 13:41 hat Michael Tokarev geschrieben:
>> Just log to stderr unconditionally, like other similar code does.
>>

>>  
>> -DLOG(if (stderr == NULL) {
>> -    stderr = fopen("vvfat.log", "a");
>> -    setbuf(stderr, NULL);
>> -})
>> -

> 
> This specific patch isn't as trivial as it might look at the first
> sight (in other words: it's wrong). The part that you probably missed is
> that stderr isn't the real one when DEBUG is set:
> 
>     #undef stderr
>     #define stderr STDERR
>     FILE* stderr = NULL;

Eeek, that's horrible.  I'd rather see code doing freopen("vvfat.log",
"a", stderr) than the current horrid mess of redefining stderr away from
its normal meaning.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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Re: [Qemu-devel] [PATCH] block/vvfat.c: remove debugging code to reinit stderr if NULL

[Kevin Wolf]

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Am 19.08.2014 um 14:06 hat Eric Blake geschrieben:
> On 08/19/2014 05:58 AM, Kevin Wolf wrote:
> > Am 18.08.2014 um 13:41 hat Michael Tokarev geschrieben:
> >> Just log to stderr unconditionally, like other similar code does.
> >>
> 
> >>  
> >> -DLOG(if (stderr == NULL) {
> >> -    stderr = fopen("vvfat.log", "a");
> >> -    setbuf(stderr, NULL);
> >> -})
> >> -
> 
> > 
> > This specific patch isn't as trivial as it might look at the first
> > sight (in other words: it's wrong). The part that you probably missed is
> > that stderr isn't the real one when DEBUG is set:
> > 
> >     #undef stderr
> >     #define stderr STDERR
> >     FILE* stderr = NULL;
> 
> Eeek, that's horrible.  I'd rather see code doing freopen("vvfat.log",
> "a", stderr) than the current horrid mess of redefining stderr away from
> its normal meaning.

I'd vote for just removing this redefine in addition to removing the
above hunk, so that everything ends up on the real stderr. But you have
to do the whole thing and not just half of it.

Kevin

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