Question

我正试图通过修改标准密钥类型，结构密钥示例来使用UTHash，该示例在以下链接中显示：

https://troydhanson.github.io/uthash/userguide.html#_structure_keys

这是我修改后的代码（向下显示以将问题隔离到哪里）

#include <stdlib.h>
#include <stdio.h>
#include <stdbool.h>
#include "uthash.h"

typedef struct StateKey
{
    // array of bools that gives the instances that are present.
    bool *instancesAtNode_BoolArray;

} t_StateKey;


typedef struct State
{
    // State Key.  
    t_StateKey stateKey_StateKey;

    // probability of being in the given state
    double p;

    // UTHash handle array used for hashing 
    UT_hash_handle hh;

} t_State;

int main(int argc, char *argv[]) {

    double a = .80;
    double b = .2;     
    double c = .1;     
    //double d = .7;    

    t_State *state, *stateHead, *toFind = NULL;
    state = (t_State *) malloc(sizeof(t_State));
    memset(state, 0, sizeof(t_State));
    state->stateKey_StateKey.instancesAtNode_BoolArray = NULL;
    state->p = 1;

    HASH_ADD(hh, stateHead, stateKey_StateKey, sizeof(t_StateKey), state);

    return 0;
}

注意，主要是我已注释掉变量d。按下面的方式运行代码没有任何问题，但是在我取消注释的那一刻，该代码引发了分段错误。对我来说，这表明发生了种种超出范围的错误，仅在代码具有特定的大小/组织时，操作系统才开始使用（这就是为什么注释掉看似无关的变量可以防止该错误的原因）。

由于我正在按照示例所提供的示例进行操作，因此我对自己在做错的事情不知所措。看着Valgrind，我得到了以下

==94553== Conditional jump or move depends on uninitialised value(s)
==94553==    at 0x10000195F: main (testNewMcUniverseMain.c:40)
==94553==  Uninitialised value was created by a stack allocation
==94553==    at 0x7FFF5FC01036: _dyld_start (in /usr/lib/dyld)
==94553== 
==94553== Use of uninitialised value of size 8
==94553==    at 0x100001A9F: main (testNewMcUniverseMain.c:40)
==94553==  Uninitialised value was created by a stack allocation
==94553==    at 0x7FFF5FC01036: _dyld_start (in /usr/lib/dyld)
==94553== 
==94553== Use of uninitialised value of size 8
==94553==    at 0x100001ABF: main (testNewMcUniverseMain.c:40)
==94553==  Uninitialised value was created by a stack allocation
==94553==    at 0x7FFF5FC01036: _dyld_start (in /usr/lib/dyld)
==94553== 
==94553== Use of uninitialised value of size 8
==94553==    at 0x100001ACB: main (testNewMcUniverseMain.c:40)
==94553==  Uninitialised value was created by a stack allocation
==94553==    at 0x7FFF5FC01036: _dyld_start (in /usr/lib/dyld)
==94553== 
==94553== Use of uninitialised value of size 8
==94553==    at 0x100001AE6: main (testNewMcUniverseMain.c:40)
==94553==  Uninitialised value was created by a stack allocation
==94553==    at 0x7FFF5FC01036: _dyld_start (in /usr/lib/dyld)
==94553== 
==94553== Invalid write of size 8
==94553==    at 0x100001AEE: main (testNewMcUniverseMain.c:40)
==94553==  Address 0x5400313d524f4c5f is not stack'd, malloc'd or 
(recently) free'd
==94553== 
==94553== Signal 11 being dropped from thread 0's queue
==94553== Signal 11 being dropped from thread 0's queue
==94553== Signal 11 being dropped from thread 0's queue
==94553== Signal 11 being dropped from thread 0's queue

(Repeats this line forever, I had to kill the terminal)

我做错了什么还是这是UTHash的问题？如果它是UTHash，那么可以用于C（不是C ++）的另一个哈希表库又是什么呢？

为简单起见，我从下面引用的源代码中复制了UTHash示例代码

#include <stdlib.h>
#include <stdio.h>
#include "uthash.h"

typedef struct {
  char a;
  int b;
}     record_key_t;

typedef struct {
    record_key_t key;
    /* ... other data ... */
    UT_hash_handle hh;
} record_t;

int main(int argc, char *argv[]) {
    record_t l, *p, *r, *tmp, *records = NULL;

    r = (record_t *)malloc(sizeof *r);
    memset(r, 0, sizeof *r);
    r->key.a = 'a';
    r->key.b = 1;
    HASH_ADD(hh, records, key, sizeof(record_key_t), r);

    memset(&l, 0, sizeof(record_t));
    l.key.a = 'a';
    l.key.b = 1;
    HASH_FIND(hh, records, &l.key, sizeof(record_key_t), p);

    if (p) printf("found %c %d\n", p->key.a, p->key.b);

    HASH_ITER(hh, records, p, tmp) {
       HASH_DEL(records, p);
       free(p);
    }
    return 0;
}

Answer 1

我有个笨蛋。

从示例

record_t l, *p, *r, *tmp, *records = NULL;

将仅初始化记录为空。由于UTHash要求将“ head”（在本例中为记录）初始化为null，因此此示例有效。在我的示例中，头是“ stateHead”，并且未初始化为null。由于某种原因，我决定

t_State *state, *stateHead, *toFind = NULL;

将所有这些指针设置为null（不是C的工作方式）。

修改使用struct作为键的示例时，UTHash分段错误

1 个答案: