Re: C++ Tracking primitive type value change

From:

=?UTF-8?B?TWFyY2VsIE3DvGxsZXI=?= <news.5.maazl@spamgourmet.com>

Newsgroups:

comp.lang.c++

Date:

Mon, 21 Jun 2010 00:16:36 +0200

Message-ID:

<4c1e9345$0$6774$9b4e6d93@newsspool3.arcor-online.net>

Hi,

ljh131 wrote:

thanks to your reply, but i can't use debugger or something because i
can't reproduce this bug.
the problem occurs only in real condition (just once or twice by many
users per day)

is your integer unmodified once the application is initialized?
If so you could run the application in the debugger the whole day with
only a data breakpoint to your integer set. If your hardware supports
that, there will be no performance impact.

so i want these techniques to solve this problem easily.

You will only capture accidental program flow this way. If you have
undefined behavior, e.g. as result of a race condition, your solution
will not trigger. Also the memory layout of your class is different from
int. This may modify the symptom.

But you can improve your class and store an shadow copy with the 1's
complement of the value. Any read access can prove the shadow for
consistency. It is very unlikely the a data bomb will keep the
consistency of the 1's complement. However, unlike a data-point this
will only trigger when the variable is read. So you might need to add
additional (unneeded) read access to your integer at certain places in
your code.

Marcel