Re: [PATCH 1/2] block/block-copy: Fix uninitialized variable in block_copy_task_entry

[Eric Blake <eblake@redhat.com>]

On 5/7/20 7:11 AM, Philippe Mathieu-Daudé wrote:
> Fix when building with -Os:
> 
>      CC      block/block-copy.o
>    block/block-copy.c: In function ‘block_copy_task_entry’:
>    block/block-copy.c:428:38: error: ‘error_is_read’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
>      428 |         t->call_state->error_is_read = error_is_read;
>          |         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~
> 

Looks like -Os triggered different inlining of block_copy_do_copy().  I 
confirm that block_copy_do_copy does NOT initialize error_is_read except 
when returning < 0, but similarly block_copy_task_entry() does not read 
error_is_read except in the same setups.  So it looks like no actual bug 
was triggered, but we can definitely aid the compiler's analysis by 
initializing.

> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> ---
>   block/block-copy.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)

Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake, Principal Software Engineer
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