* [PATCH] gdb: initialize the data_head variable to eliminate compilation warnings
@ 2022-06-11 10:36 Enze Li
2022-07-06 13:53 ` [PING] " Enze Li
0 siblings, 1 reply; 4+ messages in thread
From: Enze Li @ 2022-06-11 10:36 UTC (permalink / raw)
To: gdb-patches
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;
--
2.36.1
^ permalink raw reply [flat|nested] 4+ messages in thread
* [PING] [PATCH] gdb: initialize the data_head variable to eliminate compilation warnings
2022-06-11 10:36 [PATCH] gdb: initialize the data_head variable to eliminate compilation warnings Enze Li
@ 2022-07-06 13:53 ` Enze Li
2022-07-06 14:02 ` Metzger, Markus T
0 siblings, 1 reply; 4+ messages in thread
From: Enze Li @ 2022-07-06 13:53 UTC (permalink / raw)
To: gdb-patches; +Cc: 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;
^ permalink raw reply [flat|nested] 4+ messages in thread
* RE: [PING] [PATCH] gdb: initialize the data_head variable to eliminate compilation warnings
2022-07-06 13:53 ` [PING] " Enze Li
@ 2022-07-06 14:02 ` Metzger, Markus T
2022-07-08 13:47 ` Enze Li
0 siblings, 1 reply; 4+ messages in thread
From: Metzger, Markus T @ 2022-07-06 14:02 UTC (permalink / raw)
To: Enze Li; +Cc: enze.li, gdb-patches
Hello Enze,
>> 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;
>> | ~~~~~~~~~~~~~~~~~~^~~~~~~~~~~
That's a false positive. Since RETRIES > 0, the loop is executed at least
once and DATA_HEAD is initialized.
>> 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;
OK to pacify GCC. Thanks for the patch. LGTM.
regards,
markus.
Intel Deutschland GmbH
Registered Address: Am Campeon 10, 85579 Neubiberg, Germany
Tel: +49 89 99 8853-0, www.intel.de <http://www.intel.de>
Managing Directors: Christin Eisenschmid, Sharon Heck, Tiffany Doon Silva
Chairperson of the Supervisory Board: Nicole Lau
Registered Office: Munich
Commercial Register: Amtsgericht Muenchen HRB 186928
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PING] [PATCH] gdb: initialize the data_head variable to eliminate compilation warnings
2022-07-06 14:02 ` Metzger, Markus T
@ 2022-07-08 13:47 ` Enze Li
0 siblings, 0 replies; 4+ messages in thread
From: Enze Li @ 2022-07-08 13:47 UTC (permalink / raw)
To: Metzger, Markus T; +Cc: enze.li, gdb-patches
Hi Markus,
Thanks for your review.
On Wed, 2022-07-06 at 14:02 +0000, Metzger, Markus T wrote:
> Hello Enze,
>
> > > 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;
> > > | ~~~~~~~~~~~~~~~~~~^~~~~~~~~~~
>
> That's a false positive. Since RETRIES > 0, the loop is executed at
> least
> once and DATA_HEAD is initialized.
Yeah, that's my understanding as well.
>
>
> > > 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;
>
> OK to pacify GCC. Thanks for the patch. LGTM.
I'm checking this in now.
Thanks,
Enze
>
> regards,
> markus.
> Intel Deutschland GmbH
> Registered Address: Am Campeon 10, 85579 Neubiberg, Germany
> Tel: +49 89 99 8853-0, www.intel.de <http://www.intel.de>
> Managing Directors: Christin Eisenschmid, Sharon Heck, Tiffany Doon
> Silva
> Chairperson of the Supervisory Board: Nicole Lau
> Registered Office: Munich
> Commercial Register: Amtsgericht Muenchen HRB 186928
^ permalink raw reply [flat|nested] 4+ messages in thread
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2022-06-11 10:36 [PATCH] gdb: initialize the data_head variable to eliminate compilation warnings Enze Li
2022-07-06 13:53 ` [PING] " Enze Li
2022-07-06 14:02 ` Metzger, Markus T
2022-07-08 13:47 ` Enze Li
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