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](http://stackoverflow.com/a/3377988) — Frxstrem, Apr 19 '14 at 23:18
Unless you are always dealing with strings, won't this just overflow and segfault? — Casper Beyer, Apr 19 '14 at 23:24
Can you give an example of how the array data is set up and how you call this function? — M.M, Apr 20 '14 at 05:59

Matt · Answer 1 · 2014-04-20T14:08:23.270

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 '14 at 14:08

answered Apr 19 '14 at 23:20

Matt

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`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 Apr 20 '14 at 05:57
Also, `while(i)` will always be true and you will run off the end of your array and into la-la land – M.M Apr 20 '14 at 05:58
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. – Matt Apr 20 '14 at 14:10
1

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 . – M.M Apr 20 '14 at 14:43

Print an Array in C++ using void pointer

1 Answers1