pseudocode:
 
list<set> results;
int m;
list<int> a;
 
// ...    
 
a.sort();
 
for each i in [0..a.size]
    f(i,empty_set);    
 
// ...
 
void f(int ind,set current_set)
{
    current_set.add(a[ind]);
 
    if (current_set.sum > m)
    {
        results.add(current_set);
    }
    else
    {
        for (int i=ind + 1; i<a.size; ++i)
        {
            f(i,current_set);  // pass set by value
 
            // if prevIoUs call reached solution,no need to continue
            if (a[ind] + current_set.sum) > m
                break;
        }
    }
}
 
// choose whatever "best" result you need from results,the one
// with the lowest sum or lowest number of elements