Re: memory trampling

From:
Zeppe <zep_p@remove.all.this.long.comment.yahoo.it>
Newsgroups:
comp.lang.c++
Date:
Tue, 21 Oct 2008 16:31:53 +0100
Message-ID:
<gdkska$3op$1@aioe.org>
joshuajnoble wrote:

I threw together a quick test here, I'm thinking my problem is in what
I'm doing with the static pointer (perhaps). Here's my Singleton:


I'm not sure, I can't see major problems in this piece of code.

#ifndef SINGLETON
#define SINGLETON

class SingletonImpl
{
public:
    static SingletonImpl* getInst();
    int val1;
    char* val2[5];

protected:
        static SingletonImpl* inst;
        SingletonImpl();

};

#endif

SingletonImpl::SingletonImpl(){
    val1 = 1;
    val2 = "abcdefghijklmn";

this is maybe val2[0] = "..."; otherwise, it won't compile. However, it
will give you warning anyway regarding the conversion from const char*
(the string literal) to char*.

}

SingletonImpl* SingletonImpl::getInst(){
    if(inst == 0) {
        inst = new SingletonImpl();
    }
    return inst;
}


Surely inst is initialised somewhere to NULL, as in

SingletonImpl* SingletonImpl::inst = NULL;

or similar. Otherwise it won't link. If you don't initialise it to zero,
it will compile and crash.

TestObjs::TestObjs(char* ch){
    c = ch;
    SingletonImpl::getInst()->val2[0] = c;
}

class TestObjs {
public:
    TestObjs(char* ch);
    char* c;
};

And then my main:

int main (int argc, char * const argv[]) {
    char* c = "ghu";
    TestObjs t = TestObjs(c);
    char* c3 = "3333333";
    TestObjs t2 = TestObjs(c3);
    return 0;
}


again, only the deprecated casts from string literal to char* seem "wrong".

And this blows up...I realize this is a pretty rudimentary question
and not really on par with the normal level of discussion here so
thanks in advance for any help and your patience :)


I don't think so, really. Araprt from the fact that the level here gets
very low at times, every question is worth discussing. Check the
SingletonImpl::inst initialisation, and if it is all right, in my
opinion it should not crash, so you may want to post the complete code
that in your pc generates the error.

Best wishes,

Zeppe

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