Re: [PATCH v3] Add missing initialization for g_autofree variables

[Matthew Rosato <mjrosato@linux.ibm.com>]

On 3/15/21 6:42 AM, Cornelia Huck wrote:
> On Mon, 15 Mar 2021 11:13:52 +0100
> mrezanin@redhat.com wrote:
> 
>> From: Miroslav Rezanina <mrezanin@redhat.com>
>>
>> When declaring g_autofree variable without inicialization, compiler
>> will raise "may be used uninitialized in this function" warning due
>> to automatic free handling.
>>
>> This is mentioned in docs/devel/style.rst (quote from section
>> "Automatic memory deallocation"):
>>
>>    * Variables declared with g_auto* MUST always be initialized,
>>      otherwise the cleanup function will use uninitialized stack memory
>>
>> Add inicialization for these declarations to prevent the warning and
>> comply with coding style.
> 
> Fixes: cd7498d07fbb ("s390x/pci: Add routine to get the vfio dma available count")
> Fixes: 1e7552ff5c34 ("s390x/pci: get zPCI function info from host")
> 
> I can fix the spelling mistakes pointed out by Phil while applying, and
> also add an 's390x/pci' prefix.
> 
> Would not mind a quick test run from someone with the hardware.

Sure, I took this for a spin (ConnectX-3 VF via vfio-pci) and made sure 
both code paths were being driven without issue.  Code looks fine as well.

Tested-by: Matthew Rosato <mjrosato@linux.ibm.com>

> 
>>
>> Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
>>
>> ---
>> * v3:
>>    -- allocate in s390_pci_update_dma_avail instead of NULL init
>>
>> * v2:
>>    -- Removed fixes in hw/remote/memory.c and hw/remote/proxy.c
>>       fixed by patch sent by Zenghui Yu (multi-process: Initialize
>>       variables declared with g_auto*)
>> ---
>>   hw/s390x/s390-pci-vfio.c | 9 +++------
>>   1 file changed, 3 insertions(+), 6 deletions(-)
>>
>> diff --git a/hw/s390x/s390-pci-vfio.c b/hw/s390x/s390-pci-vfio.c
>> index ead4f222d5..2a153fa8c9 100644
>> --- a/hw/s390x/s390-pci-vfio.c
>> +++ b/hw/s390x/s390-pci-vfio.c
>> @@ -29,14 +29,11 @@
>>    */
>>   bool s390_pci_update_dma_avail(int fd, unsigned int *avail)
>>   {
>> -    g_autofree struct vfio_iommu_type1_info *info;
>> -    uint32_t argsz;
>> +    uint32_t argsz = sizeof(struct vfio_iommu_type1_info);
>> +    g_autofree struct vfio_iommu_type1_info *info = g_malloc0(argsz);
>>   
>>       assert(avail);
>>   
>> -    argsz = sizeof(struct vfio_iommu_type1_info);
>> -    info = g_malloc0(argsz);
>> -
>>       /*
>>        * If the specified argsz is not large enough to contain all capabilities
>>        * it will be updated upon return from the ioctl.  Retry until we have
>> @@ -230,7 +227,7 @@ static void s390_pci_read_pfip(S390PCIBusDevice *pbdev,
>>    */
>>   void s390_pci_get_clp_info(S390PCIBusDevice *pbdev)
>>   {
>> -    g_autofree struct vfio_device_info *info;
>> +    g_autofree struct vfio_device_info *info = NULL;
>>       VFIOPCIDevice *vfio_pci;
>>       uint32_t argsz;
>>       int fd;
>