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


From: Christian Borntraeger
Subject: Re: [PATCH 1/4] vmdk: fix maybe uninitialized warnings
Date: Mon, 5 Oct 2020 08:26:26 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.12.0

On 30.09.20 18:36, Fam Zheng wrote:
> 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>


Will this go via the block or trivial tree (cced). 



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