带有char*键的C++无序映射会产生意外行为

我试图使用一个无序映射将char*键散列为一个整数值。在编写了自定义函数来散列和比较char*之后，无序映射似乎可以工作了。然而，我最终注意到散列偶尔会返回不正确的结果。我创建了一个测试项目来重现错误。下面的代码创建了一个带有char*键和自定义函数的无序映射。然后，它运行1000x个循环，并记录发生的任何哈希错误。我想知道我的函子是否有问题，或者问题是否存在于无序映射中。如有任何帮助，我们将不胜感激。谢谢

#include <cstdlib>
#include <stdio.h>
#include <string.h>
#include <time.h>
#include <tr1/unordered_map>
using namespace std;
//These varaibles are just used for printing the status.
static const char* c1;
static const char* c2;
static int cmpRet;
static int cmpVal;
static const char* hashChar;
static size_t hashVal;
// Character compare functor.
struct CmpChar {
  bool operator()(const char* s1, const char* s2) const {
    c1 = s1;
    c2 = s2;
    cmpVal = strcmp(s1, s2);
    cmpRet = (cmpVal == 0);
    return cmpRet;
  }
};
// Hash functor.
struct HashChar {
  size_t operator()(const char* str) const {
    hashChar = str;
    size_t hash = 0;
    int c;
    while (c = *str++)
      hash = c + (hash << 6) + (hash << 16) - hash;
    hashVal = hash;
    return hash;
  }
};
void printStatus() {
  printf("'%s' was hashed to: '%lu'n", hashChar, hashVal);
  printf("strcmp('%s','%s')='%d' and KeyEqual='%d'n", c1, c2, cmpVal, cmpRet);
}
int main(int argc, char** argv) {
  // Create the unordered map.
  tr1::unordered_map<const char*, int, HashChar, CmpChar > hash_map;
  hash_map["apple"] = 1;
  hash_map["banana"] = 2;
  hash_map["orange"] = 3;
  // Grab the inital hash value of 'apple' to see what it hashes to.
  char buffer[256];
  bzero(buffer, sizeof (buffer));
  strcpy(buffer, "apple");
  if (hash_map[buffer] == 1) {
    printf("First hash: '%s'=1n", buffer);
  }
  printStatus();
  // Create a random character
  srand((unsigned int) time(NULL));
  char randomChar = (rand() % 26 + 'a');
  // Use the hash 1000x times to see if it works properly.
  for (int i = 0; i < 1000; i++) {
    // Fill the buffer with 'apple'
    bzero(buffer, sizeof (buffer));
    strcpy(buffer, "apple");
    // Try to get the value for 'apple' and report an error if it equals zero.
    if (hash_map[buffer] == 0) {
      printf("n****Error: '%s'=0 ****n", buffer);
      printStatus();
    }
    // Fill the buffer with a random string.
    bzero(buffer, sizeof (buffer));
    buffer[0] = randomChar;
    buffer[1] = '';
    // Hash the random string.
    // ** Taking this line out removes the error. However, based on the functors
    // it should be acceptable to reuse a buffer with different content.
    hash_map[buffer];
    // Update the random character.
    randomChar = (rand() % 26 + 'a');
  }
  printf("done!n");
  return EXIT_SUCCESS;
}