Deleting pointer to array

Question

In one of my large projects I encountered problem with deleting arrays that were initialized with no specified size.
I wrote a simple program to check what is going wrong, here is the code

#include "stdafx.h"

class Checker
{
public:
    Checker()
    :myI(i++){}

virtual ~Checker(){
    printf("%i " , myI);
    fflush(stdout);
}
private:
    int myI;
    static int i;
};

int Checker::i = 0;


int _tmain(int argc, _TCHAR* argv[]){
    Checker* somePointer;
    Checker* anotherPointer;

    somePointer = new Checker[4]{
        Checker(), Checker(), Checker(), Checker()};

    anotherPointer = new Checker[]{
        Checker(), Checker(), Checker(), Checker()};

    delete[] somePointer;

    delete[] anotherPointer; //approach A
    delete anotherPointer; //approach B
    //in approach C anotherPointer is not deleted

    return 0;
}

As You can see anotherPointer is initialized without explicitly defined size.
Of course, only one of the lines marked as approach is active at once.
In approach A output looks like that (< crash> means that program ends unexpectedly)

 3 2 1 0 <crash>

In approach B output is

 3 2 1 0 4 <crash>

In approach C some time the output is 3 2 1 0 and other time application crashes without printing anything.

As far as I know initialization without specifying size of array ends with different memory allocation, but i don't know how to solve problem with application that crashes at the end and this is my question.

I'm using Visual Studio Pro 2013 Update 4 (MSVC++)

EDIT
In case that there is no solution to that problem other than explicitly specifying size, my question is
Why that "feature" is implemented in MSCC++ at all?

What do you mean by ends unexpectedly? Do you get an error message? — Benjy Kessler
– Benjy Kessler, Commented May 5, 2015 at 23:36
g++ fails to compile your sample code, even after getting rid of the obvious MS-ism; issuing a diagnostic for "new Checker[]{". This appears to be relying on non-portable, compiler-specific feature or behavior, and not standard C++. — Sam Varshavchik
– Sam Varshavchik, Commented May 5, 2015 at 23:38
Standard C++'s grammar does not seem to allow new Checker[] with empty brackets. — sh03
– sh03, Commented May 5, 2015 at 23:40
Accepting it looks like a pretty clear-cut compiler bug. For what it's worth, the preview of VC++ 2015 rejects it with an error message saying: error C3078: you cannot 'new' an array of unknown bounds. — Jerry Coffin
– Jerry Coffin, Commented May 6, 2015 at 6:35
@Jefffrey: It might (or might not) be worth noting that even with the empty brackets, it is almost amazingly close to being syntactically correct (but as a lambda expression). — Jerry Coffin
– Jerry Coffin, Commented May 6, 2015 at 6:44

dened · Accepted Answer · 2015-05-12 14:49:35Z

2

Currently C++ standard doesn't allow allocation of arrays without explicitly specified size (like you can in Java or C#). GCC C++ and Clang both give an error while trying to compile you code (even in C++14 mode). Visual Studio 2015 RC also produces error C3078: you cannot 'new' an array of unknown bounds. Summarizing, it's not a feature, it's a bug in VS 2013 what apparently was fixed in VS 2015.

answered May 12, 2015 at 14:49

dened

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