On Aug 20, 8:10 pm, Bill Hart <[EMAIL PROTECTED]> wrote:
> Getting rid of memory leaks also speeds up code dramatically as I
> found out recently. When new memory is allocated by the kernel, it
> isn't quite ready to be used. As you begin writing to it, pages of
> roughly 4kb at a time initiate an interrupt which the kernel has to
> deal with, called a minor page fault. These take quite some time to
> deal with. So using more and more memory results in more and more
> minor page faults. So there is definite benefit in killing memory
> leaks, even less serious ones.
>
Hey Bill,
> However, there is one "error" which valgrind reports on my own code
> from time to time which I have been unable to determine the source of.
> It says something like "conditional jump depends on uninitialised
> data". I have stared at code for hours trying to determine where these
> errors come from. I still have code for which I have been unable to
> eliminate such errors.
>
That usually happens in the following circumstance:
int i; // this is initialized to zero on any sane system, i.e.
anywhere but Windows :)
if (i>0)
do something;
Now valgrind assumes that "conditional jump depends on uninitialised
data", i.e. "i". Well, but it is zero anyway would one say. And you
would be correct in 99% of all cases, but I fixed a bug very similar
to the above in LinBox about 4 weeks ago that caused a crash on Debian
unstable's gcc but not with the other 10 compilers I tried. Lesson
lerned. The assigment to zero puts i into another segment, so many
people avoid it.
> I understand the meaning of the error as such, but couldn't determine
> why valgrind thought that part of my code contained such an error.
> Perhaps valgrind is not infallible, or perhaps I've been missing
> something.
>
> Bill.
>
Cheers,
Michael
<SNIP>
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