Re: [Qemu-devel] [PATCH v3 09/12] tests/libqos/pci: Clean up string interpolation into QMP input

[Eric Blake]

On 07/28/2017 08:05 AM, Stefan Hajnoczi wrote:
> On Tue, Jul 25, 2017 at 04:15:20PM -0500, Eric Blake wrote:
>> @@ -419,19 +420,18 @@ static void test_ivshmem_server_irq(void)
>>  static void test_ivshmem_hotplug(void)
>>  {
>>      const char *arch = qtest_get_arch();
>> -    gchar *opts;
>> +    QObject *extra_args = qobject_from_jsonf("{ 'shm': '%s', 'size': '1M' 
>> }",
>> +                                             tmpshm);
> 
> Is there a difference between:
> 
>   qobject_from_jsonf("{ 'shm': '%s' }", tmpshm);
> 
> and:
> 
>   qobject_from_jsonf("{ 'shm': %s }", tmpshm);

Yes, and it's important.

sprintf("{ 'shm': '%s' }", tmpshm);

is the same as

qobject_from_jsonf("{ 'shm': %s }" tmpshm);

Passing '%s' through qobject_from_jsonf() is generally wrong (it would
produce ''...'' instead of the intended '...').

Looks like something to fix on the next round.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org

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