Re: [PATCH 1/4] vmdk: fix maybe uninitialized warnings

[Fam Zheng]

On Wed, 2020-09-30 at 17:58 +0200, Christian Borntraeger wrote:
> Fedora 32 gcc 10 seems to give false positives:
> 
> Compiling C object libblock.fa.p/block_vmdk.c.o
> ../block/vmdk.c: In function ‘vmdk_parse_extents’:
> ../block/vmdk.c:587:5: error: ‘extent’ may be used uninitialized in
> this function [-Werror=maybe-uninitialized]
>   587 |     g_free(extent->l1_table);
>       |     ^~~~~~~~~~~~~~~~~~~~~~~~
> ../block/vmdk.c:754:17: note: ‘extent’ was declared here
>   754 |     VmdkExtent *extent;
>       |                 ^~~~~~
> ../block/vmdk.c:620:11: error: ‘extent’ may be used uninitialized in
> this function [-Werror=maybe-uninitialized]
>   620 |     ret = vmdk_init_tables(bs, extent, errp);
>       |           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> ../block/vmdk.c:598:17: note: ‘extent’ was declared here
>   598 |     VmdkExtent *extent;
>       |                 ^~~~~~
> ../block/vmdk.c:1178:39: error: ‘extent’ may be used uninitialized in
> this function [-Werror=maybe-uninitialized]
>  1178 |             extent->flat_start_offset = flat_offset << 9;
>       |             ~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~
> ../block/vmdk.c: In function ‘vmdk_open_vmdk4’:
> ../block/vmdk.c:581:22: error: ‘extent’ may be used uninitialized in
> this function [-Werror=maybe-uninitialized]
>   581 |     extent->l2_cache =
>       |     ~~~~~~~~~~~~~~~~~^
>   582 |         g_malloc(extent->entry_size * extent->l2_size *
> L2_CACHE_SIZE);
>       |         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> ~~~~~~~~~
> ../block/vmdk.c:872:17: note: ‘extent’ was declared here
>   872 |     VmdkExtent *extent;
>       |                 ^~~~~~
> ../block/vmdk.c: In function ‘vmdk_open’:
> ../block/vmdk.c:620:11: error: ‘extent’ may be used uninitialized in
> this function [-Werror=maybe-uninitialized]
>   620 |     ret = vmdk_init_tables(bs, extent, errp);
>       |           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> ../block/vmdk.c:598:17: note: ‘extent’ was declared here
>   598 |     VmdkExtent *extent;
>       |                 ^~~~~~
> cc1: all warnings being treated as errors
> make: *** [Makefile.ninja:884: libblock.fa.p/block_vmdk.c.o] Error 1
> 
> fix them by assigning a default value.
> 
> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
> ---
>  block/vmdk.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/block/vmdk.c b/block/vmdk.c
> index 8ec62c7ab798..a00dc00eb47a 100644
> --- a/block/vmdk.c
> +++ b/block/vmdk.c
> @@ -595,7 +595,7 @@ static int vmdk_open_vmfs_sparse(BlockDriverState
> *bs,
>      int ret;
>      uint32_t magic;
>      VMDK3Header header;
> -    VmdkExtent *extent;
> +    VmdkExtent *extent = NULL;
>  
>      ret = bdrv_pread(file, sizeof(magic), &header, sizeof(header));
>      if (ret < 0) {
> @@ -751,7 +751,7 @@ static int vmdk_open_se_sparse(BlockDriverState
> *bs,
>      int ret;
>      VMDKSESparseConstHeader const_header;
>      VMDKSESparseVolatileHeader volatile_header;
> -    VmdkExtent *extent;
> +    VmdkExtent *extent = NULL;
>  
>      ret = bdrv_apply_auto_read_only(bs,
>              "No write support for seSparse images available", errp);
> @@ -869,7 +869,7 @@ static int vmdk_open_vmdk4(BlockDriverState *bs,
>      uint32_t magic;
>      uint32_t l1_size, l1_entry_sectors;
>      VMDK4Header header;
> -    VmdkExtent *extent;
> +    VmdkExtent *extent = NULL;
>      BDRVVmdkState *s = bs->opaque;
>      int64_t l1_backup_offset = 0;
>      bool compressed;
> @@ -1088,7 +1088,7 @@ static int vmdk_parse_extents(const char *desc,
> BlockDriverState *bs,
>      BdrvChild *extent_file;
>      BdrvChildRole extent_role;
>      BDRVVmdkState *s = bs->opaque;
> -    VmdkExtent *extent;
> +    VmdkExtent *extent = NULL;
>      char extent_opt_prefix[32];
>      Error *local_err = NULL;
>  

Looks trivial, and correct.

Reviewed-by: Fam Zheng <fam@euphon.net>