Print an Array in C++ using void pointer

Question

I am building a DirectX game, in which I have a Debug::Log static function defined in the Debug class. This just prints the values of the passed parameter on the output/console. I want to implement a function where I can pass a starting pointer to the array(that I want to print), and print all elements in the array. However I want to let the function be flexible with the type of params passed. So, I am doing something like this..

static void DebugArray(void* pointerToArray) {
    std::stringstream ss;
    ss << "\n";

    void *i = pointerToArray;
    int k = 0;
    while(i) {
        ss << i; //This is how I am storing the array's elements
        i++; //Error in VS 2012 expression must be a pointer to a complete object type  

    }
    print(ss.str());
}

Is this is valid way of doing the intended work? How should I approach this? Any suggestions

See the accepted answer to this question: Void pointer arithmetic — Freyja
– Freyja, Commented Apr 19, 2014 at 23:18
Unless you are always dealing with strings, won't this just overflow and segfault? — Casper Beyer
– Casper Beyer, Commented Apr 19, 2014 at 23:24
Can you give an example of how the array data is set up and how you call this function? — M.M
– M.M, Commented Apr 20, 2014 at 5:59

Matt · Accepted Answer · 2014-04-20 14:08:23Z

2

Type needs to be known at compile time, so you'll need to use a template instead.

template <class T>
static void DebugArray(T* pointerToArray) {
    std::stringstream ss;
    ss << "\n";

    T *i = pointerToArray;
    int k = 0;
    while(i) {
        ss << *i; //This is how I am storing the array's elements
        i++; //Error in VS 2012 expression must be a pointer to a complete object type  

    }
    print(ss.str());
}

edited Apr 20, 2014 at 14:08

answered Apr 19, 2014 at 23:20

Matt

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4 Comments

M.M Over a year ago

ss << i just stores the pointer value. It does not access the objects being pointed-to (unless T is char ; std::ostream has an overload for char which reads a string from the pointed-to space)

M.M Over a year ago

Also, while(i) will always be true and you will run off the end of your array and into la-la land

Matt Over a year ago

Thanks @mattmcnabb, added dereference of the array element. It's always possible that the array referred to is null terminated. I just modified the ops code to work as they'd written it. They need to figure out how to stop price ting elements.

M.M Over a year ago

Even if the array is null-terminated, while(i) never terminates , incrementing a non-null pointer never makes it null. You could try while(*i) but we don't know if T has a conversion to bool. Hopefully OP can clarify .

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