test qgraph.c: Fix segs due to out of scope default

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

The test uses the trick:
   if (!opts) {
     opts = &(QOSGraph...Options) { };
   }

  in a couple of places, however the temporary created
by the &() {}  goes out of scope at the bottom of the if,
and results in a seg or assert when opts-> fields are
used (on fedora 30's gcc 9).

Fixes: fc281c802022cb3a73a5
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
---
 tests/libqos/qgraph.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

On 4/5/19 1:40 PM, Dr. David Alan Gilbert (git) wrote:
> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> 
> The test uses the trick:
>    if (!opts) {
>      opts = &(QOSGraph...Options) { };
>    }
> 
>   in a couple of places, however the temporary created
> by the &() {}  goes out of scope at the bottom of the if,
> and results in a seg or assert when opts-> fields are
> used (on fedora 30's gcc 9).
> 
> Fixes: fc281c802022cb3a73a5
> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> ---
>  tests/libqos/qgraph.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)

Fixing it for 4.0 would be nice (we can't promise that everything in 4.0
is clean for gcc 9, but as long as we have to do -rc3 anyways, fixing
undefined behavior into something well-defined like this seems reasonable)

Reviewed-by: Eric Blake <eblake@redhat.com>

On 05/04/19 20:40, Dr. David Alan Gilbert (git) wrote:
> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> 
> The test uses the trick:
>    if (!opts) {
>      opts = &(QOSGraph...Options) { };
>    }
> 
>   in a couple of places, however the temporary created
> by the &() {}  goes out of scope at the bottom of the if,
> and results in a seg or assert when opts-> fields are
> used (on fedora 30's gcc 9).
> 
> Fixes: fc281c802022cb3a73a5
> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

Thomas, can you pick this up?

Paolo

> ---
>  tests/libqos/qgraph.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/tests/libqos/qgraph.c b/tests/libqos/qgraph.c
> index 122efc1b7b..b149caaaa9 100644
> --- a/tests/libqos/qgraph.c
> +++ b/tests/libqos/qgraph.c
> @@ -77,6 +77,7 @@ static void add_edge(const char *source, const char *dest,
>  {
>      char *key;
>      QOSGraphEdgeList *list = g_hash_table_lookup(edge_table, source);
> +    QOSGraphEdgeOptions def_opts = { };
>  
>      if (!list) {
>          list = g_new0(QOSGraphEdgeList, 1);
> @@ -85,7 +86,7 @@ static void add_edge(const char *source, const char *dest,
>      }
>  
>      if (!opts) {
> -        opts = &(QOSGraphEdgeOptions) { };
> +        opts = &def_opts;
>      }
>  
>      QOSGraphEdge *edge = g_new0(QOSGraphEdge, 1);
> @@ -590,9 +591,10 @@ void qos_add_test(const char *name, const char *interface,
>  {
>      QOSGraphNode *node;
>      char *test_name = g_strdup_printf("%s-tests/%s", interface, name);;
> +    QOSGraphTestOptions def_opts = { };
>  
>      if (!opts) {
> -        opts = &(QOSGraphTestOptions) { };
> +        opts = &def_opts;
>      }
>      node = create_node(test_name, QNODE_TEST);
>      node->u.test.function = test_func;
>

On 05/04/2019 23.16, Paolo Bonzini wrote:
> On 05/04/19 20:40, Dr. David Alan Gilbert (git) wrote:
>> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
>>
>> The test uses the trick:
>>    if (!opts) {
>>      opts = &(QOSGraph...Options) { };
>>    }
>>
>>   in a couple of places, however the temporary created
>> by the &() {}  goes out of scope at the bottom of the if,
>> and results in a seg or assert when opts-> fields are
>> used (on fedora 30's gcc 9).
>>
>> Fixes: fc281c802022cb3a73a5
>> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> 
> Thomas, can you pick this up?

Sure, queued it to my qtest-next branch now:

 https://gitlab.com/huth/qemu/tree/qtest-next

I'll send a PULL request on Monday.

 Thomas