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

From: Cornelia Huck <cohuck@redhat.com>
To: mrezanin@redhat.com
Cc: qemu-s390x@nongnu.org, Thomas Huth <thuth@redhat.com>,
	qemu-devel@nongnu.org, Matthew Rosato <mjrosato@linux.ibm.com>
Subject: Re: [PATCH v3] Add missing initialization for g_autofree variables
Date: Mon, 15 Mar 2021 11:42:32 +0100	[thread overview]
Message-ID: <20210315114232.4bb6654e.cohuck@redhat.com> (raw)
In-Reply-To: <20210315101352.152888-1-mrezanin@redhat.com>

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.

> 
> 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;