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copied!<p>The question is tagged C++, and yet the answers only use the C subset...</p> <p>Well, first of all, I would recommend against the whole thing. Create a class that encapsulates your matrix and allocate it in a single block, offer <code>operator()(int,int)</code> to gain access to the elements...</p> <p>But back to the problem. In C++ you should use references rather than pointers to allow the function to change the argument, so your original allocate signature should be:</p> <pre><code>void AllocMat(int **&mat, int size); </code></pre> <p>And call it like:</p> <pre><code>int **matrix = 0; AllocMat( matrix, 5 ); </code></pre> <p>Or better, just <em>return</em> the pointer:</p> <pre><code>int **AllocMat( int size ); int **matrix = AllocMat( 5 ); </code></pre> <p>For the deallocation function, since you don't need to modify the outer pointer, you can just use:</p> <pre><code>void DeallocMat( int**mat, int size ); // size might be required to release the // internal pointers </code></pre> <p>Now, for a sketch of the C++ solution:</p> <pre><code>template <typename T> // no need to limit this to int class square_matrix { const unsigned size; T * data; public: square_matrix( unsigned size ) : size(size), data( new T[size*size]() ) {} square_matrix( matrix const & m ) : size( m.size ), data( new T[m.size*m.size] ) { std::copy( m.data, m.data+size*size, data ); } ~matrix() { delete [] data; } T const & operator()( unsigned x, unsigned y ) const { // optional range check and throw exception return data[ x + y*size ]; } void set( unsigned x, unsigned y, T const & value ) { // optional range check and throw exception data[ x + y*size ] = value; } }; </code></pre>

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