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Re: [PATCH v2] Add missing initialization for g_autofree variables


From: Thomas Huth
Subject: Re: [PATCH v2] Add missing initialization for g_autofree variables
Date: Mon, 15 Mar 2021 09:08:01 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.0

On 15/03/2021 09.00, 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 to NULL for these declaration to prevent this
warning.

Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>

---
* From v1:
   -- 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 | 4 ++--
  1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/hw/s390x/s390-pci-vfio.c b/hw/s390x/s390-pci-vfio.c
index ead4f222d5..0ee7dc21f2 100644
--- a/hw/s390x/s390-pci-vfio.c
+++ b/hw/s390x/s390-pci-vfio.c
@@ -29,7 +29,7 @@
   */
  bool s390_pci_update_dma_avail(int fd, unsigned int *avail)
  {
-    g_autofree struct vfio_iommu_type1_info *info;
+    g_autofree struct vfio_iommu_type1_info *info = NULL;
      uint32_t argsz;
assert(avail);

I'd maybe rather rework the functions like this:

diff --git a/hw/s390x/s390-pci-vfio.c b/hw/s390x/s390-pci-vfio.c
index ead4f222d5..1fe71fd93f 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 +230,7 @@ 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;


Anyway,
Reviewed-by: Thomas Huth <thuth@redhat.com>




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