I've been toying a bit with C++. That language is probably better suited for what I want. Here's the code (for gcc):

#include <iostream>
#include <ext/hash_map>
#include <vector>

using namespace std;

/*
 * hash function, borrowed from
 * http://burtleburtle.net/bob/c/lookup3.c
 */

#define rot(x,k) (((x)<<(k)) | ((x)>>(32-(k))))

#define mix(a,b,c) \
{ \
  a -= c;  a ^= rot(c, 4);  c += b; \
  b -= a;  b ^= rot(a, 6);  a += c; \
  c -= b;  c ^= rot(b, 8);  b += a; \
  a -= c;  a ^= rot(c,16);  c += b; \
  b -= a;  b ^= rot(a,19);  a += c; \
  c -= b;  c ^= rot(b, 4);  b += a; \
}

#define final(a,b,c) \
{ \
  c ^= b; c -= rot(b,14); \
  a ^= c; a -= rot(c,11); \
  b ^= a; b -= rot(a,25); \
  c ^= b; c -= rot(b,16); \
  a ^= c; a -= rot(c,4);  \
  b ^= a; b -= rot(a,14); \
  c ^= b; c -= rot(b,24); \
}
struct hashword
{
  size_t operator()(const vector<uint32_t>* k) const { 
    uint32_t a, b, c;
    size_t length = (*k).size();
    uint32_t initval = 0;
    unsigned int ki = 0;

    /* Set up the internal state */
    a = b = c = 0xdeadbeef + (((uint32_t) length) << 2) + initval;

    /*------------------------------ handle most of the key */
    while (length > 3) {
        a += (*k)[ki++];
        b += (*k)[ki++];
        c += (*k)[ki++];
        mix(a,b,c);
        length -= 3;
    }

    ki = (*k).size() - 1;

    /*-------------------------------- handle the last 3 uint32_t's */
    switch (length) /* all the case statements fall through */
    {
    case 3:
        c += (*k)[ki--];
    case 2:
        b += (*k)[ki--];
    case 1:
        a += (*k)[ki];
        final(a,b,c)
        ;
    case 0: /* case 0: nothing left to add */
        break;
    }
    /*-------------------------------------- report the result */

    return c;
  }
};

/* compare 2 vectors */
struct eqintarr
{
  bool operator()(const vector<uint32_t>* s1, const vector<uint32_t>* 
+s2) const
  {
    return (*s1 == *s2);
  }
};

int main()
{
  __gnu_cxx::hash_map<const vector<uint32_t>*, int, hashword, eqintarr
+> preds;

  uint32_t a[] = {1,2,3,4,5};
  uint32_t b[] = {0,34567,3,5,256001};

  vector<uint32_t> k1 (a, a + sizeof(a) / sizeof(uint32_t) );
  vector<uint32_t> k2 (k1);

  vector<uint32_t> k3 (b, b + sizeof(b) / sizeof(uint32_t) );
  vector<uint32_t> k4 (k3);

  preds[&k1] = 7;
  preds[&k3] = 100;

  cout << "k1 -> " << preds[&k2] << endl;
  cout << "k2 -> " << preds[&k4] << endl;
}
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