Re: allocate 2d pointer. is ths a bug ?

[h]

Thanks Bernd Strieder !

i've tried like this already.

<code>
$ g++ -o test test.cpp -Wall -ansi -pedantic"
</code>

 i didn't see any warning.

but, i'm tring use let me known optimizing option "-O2" and i can see 
warning from g++ exactly.
<code>
$ g++ -o test test.cpp -Wall -ansi -pedantic -O2"
test.cpp: In function `int main()':
test.cpp:5: warning: 'str' might be used uninitialized in this function
</code>
so, cause i could see warning from VC++ 6.0, it has an optimizing option 
already.

Thanks.

Regards,
godmode2k at hotmail.com
from KLDP.org


"Bernd Strieder" <strieder@informatik.uni-kl.de> wrote in message 
news:ebfaas$h2j$1@news.uni-kl.de...
>h wrote:
>
>> Thanks Mehturt.
>>
>> but, it works through g++ on Cygwin and GNU/Linux machine without
>> MS-VC++ 6.0 on win32 machine.
>> i know i've attached code are has a problem.
>>
>> okay, i wanna know exactly attached code are why looks working good in
>> g++ only.
>> that's it.
>
> I cannot reproduce the exact behaviour. The app crashes at different
> places depending on optimization.
>
> If you compile with optimization and warnings turned on, then g++ will
> tell you something (g++ -O2 -Wall ...). If you want to know exactly
> what happens, you have to use a debugger to look what the values are
> initialized to. Or you have to insert some more output. But don't be
> surprised, if behaviour changes completely, when you do so. This is the
> very nature of undefined behaviour, it can be like a phantom. You have
> done a simple bug and it will bug you for weeks, randomly. This is why
> it is so nice that the compiler can warn you about missing
> initializations.
>
> I think it is prossible to create both kinds of apps with undefined
> behaviour on all platforms, non-crashing and crashing ones. The
> differences are subtle, and you have to dig deeply into the whole
> runtime system to understand. You need about the expertise a hacker
> uses to break into some application.
>
> There is no point in looking for the exact cause, that undefined
> behaviour does not result in a crash, just remove the bug and be happy,
> and remember next time you declare a pointer to initialize, and
> remember to turn warnings on next time you compile.
>
> Bernd Strieder
>