Re: delete POD array - on which platforms does it not work?

From:
"Bo Persson" <bop@gmb.dk>
Newsgroups:
comp.lang.c++
Date:
Wed, 2 Apr 2008 19:20:04 +0200
Message-ID:
<65hthcF2fvuj8U1@mid.individual.net>
Triple-DES wrote:

On 2 Apr, 10:47, Juha Nieminen <nos...@thanks.invalid> wrote:

Martin T. wrote:

Krice wrote:

On 2 huhti, 08:30, "Martin T." <0xCDCDC...@gmx.at> wrote:

delete p; // will work on VC8
free(p); // will also work on VC8


Are you sure these don't mess up anything in VC8?


Yes, 100% sure.


How can you be so sure? Are you sure that they don't, for example,
leak memory? Did you use some kind of profiler to check this or
something?


The _CrtDumpMemoryLeaks() function can be used when running under
the debugger. I too tried this, and was unable to produce a memory
leak on VC8.


How many times did you run the test, and under what conditions?

What if it only fails first Wednesday after a full moon on leap years,
and only if an important customer is watching. That's usually when
Undefined Behavior goes bad.

Without further evidence, I wouldn't go as far as saying that this
is 100% safe on VC8, but it would seem that the most trivial cases
are handled gracefully.


It actually does work, but just by chance. Usually new[] has to store
a count, so the system can later know how many times delete[] has to
call the destructor for the objects in the array. As a space
optimization, the count is not stored for objects without a
destructor, so by pure chance a char[10] object has the same layout as
any other 10 byte memory block.

Do you want to rely on this??

Bo Persson

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