[PING] [PATCH] gdb: initialize the data_head variable to eliminate compilation warnings

[Enze Li]

Hi all,

Kindly PING for this tiny patch.  The warning mentioned in this patch
still exists in the trunk.  Does it make sense?

Best Regards,
Enze

On Sat, 2022-06-11 at 18:36 +0800, Enze Li via Gdb-patches wrote:
> On a machine with gcc 12, I get this warning:
> 
>   CXX    nat/linux-btrace.o
> In function ‘btrace_error linux_read_bts(btrace_data_bts*,
> btrace_target_info*, btrace_read_type)’,
>     inlined from ‘btrace_error linux_read_btrace(btrace_data*,
> btrace_target_info*, btrace_read_type)’ at ../gdb/nat/linux-
> btrace.c:935:29:
> ../gdb/nat/linux-btrace.c:865:21: warning: ‘data_head’ may be used
> uninitialized [-Wmaybe-uninitialized]
>   865 |   pevent->last_head = data_head;
>       |   ~~~~~~~~~~~~~~~~~~^~~~~~~~~~~
> ../gdb/nat/linux-btrace.c: In function ‘btrace_error
> linux_read_btrace(btrace_data*, btrace_target_info*,
> btrace_read_type)’:
> ../gdb/nat/linux-btrace.c:792:9: note: ‘data_head’ was declared here
>   792 |   __u64 data_head, data_tail;
>       |         ^~~~~~~~~
> 
> Fix this by initializing the 'data_head' variable.
> 
> Tested by rebuilding on x86_64 openSUSE Tumbleweed with gcc 12.
> ---
>  gdb/nat/linux-btrace.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/gdb/nat/linux-btrace.c b/gdb/nat/linux-btrace.c
> index b0d6dcd7cf1..c31fb5ffe43 100644
> --- a/gdb/nat/linux-btrace.c
> +++ b/gdb/nat/linux-btrace.c
> @@ -789,7 +789,7 @@ linux_read_bts (struct btrace_data_bts *btrace,
>    struct perf_event_buffer *pevent;
>    const uint8_t *begin, *end, *start;
>    size_t buffer_size, size;
> -  __u64 data_head, data_tail;
> +  __u64 data_head = 0, data_tail;
>    unsigned int retries = 5;
>  
>    pevent = &tinfo->variant.bts.bts;