Re: [Valgrind-users] Address 0xNNNNN is N bytes inside a block of size N alloc'd

[Bart V. A. <bar...@gm...>]

On Mon, Jul 27, 2009 at 7:24 PM, Pavel Shevaev<pac...@gm...> wrote:
> On Mon, Jul 27, 2009 at 2:55 PM, Bart Van
> Assche<bar...@gm...> wrote:
>> On Mon, Jul 27, 2009 at 12:42 PM, Pavel Shevaev<pac...@gm...> wrote:
>>> Folks, could you please tell what exactly this error message mean? I
>>> googled around the documentation and found nothing...
>>
>> The text you quoted in the title of this e-mail is not an error
>> message by itself, but a clarification of the error message printed
>> above that message. It would help if you could post the entire
>> message.
>
> Thanks for the quick reply! For example, I have the following lines in
> valgrind log:
>
> ==31513== Thread 3:
> ==31513== Syscall param socketcall.sendmsg(msg.msg_iov[i]) points to
> uninitialised byte(s)
> ......
> (lot's of lines looking like this)
> ==31513==    by 0x59549EA:
> ......
> ==31513==  Address 0xad39096 is 86 bytes inside a block of size 32,444 alloc'd
> .....
> (some more lines)

It can be challenging to find out the cause of such error messages.
Sometimes this message is caused by uninitialized padding bytes. If
you don't find the cause via source reading, you can check the data
passed to the system call sendmsg() via the
VALGRIND_CHECK_MEM_IS_DEFINED() client request. See also the header
file /usr/include/valgrind/memcheck.h for more information.

Bart.