C 标记化字符串循环内存错误

我在一个数组中循环，试图获取每个令牌并插入到另一个字符串数组（char**），我从valgrind得到了无效的写操作以及未初始化值的使用。我该如何解决这个问题

        char *tstring;
        int i = 0;
        char **tokens = (char **)malloc(sizeof(contents));
        tstring = strtok(contents, "\"(),-> ");
        printf("sizeof(tstring) = %ld\tsizeof(*tstring) = %ld\nsizeof(contents) = %ld\n", sizeof(tstring), sizeof(*tstring), sizeof(contents));
        tokens[i] = (char*)malloc(sizeof(tstring));
        printf("tstring address: %p\ntokens address: %p\ntokens[i] address: %p\n",tstring,tokens, tokens[i]);
        strcpy(tokens[i], tstring);
        printf("token[0]: %s\n", tokens[i]);
        while( tokens[i] != NULL ) {
                i++;
                tstring = strtok(NULL, "\"(),-> ");
                if(tstring != NULL)
                        printf("token[%d]: %s\n", i, tstring);
                tokens[i] = (char*)malloc(sizeof(tstring));
                strcpy(tokens[i], tstring);
        }

下面是正在标记的字符串

"a" -> ("boo", 1), ("baa", 1)
"baa" -> ("baa", 1)
"boo" -> ("boo", 1)
"cat" -> ("baa", 1)
"dog" -> ("boo", 1)
"name" -> ("boo", 2), ("baa", 1)

这是valgrind的输出

sizeof(tstring) = 8 sizeof(*tstring) = 1
sizeof(contents) = 8
tstring address: 0x51f1041
tokens address: 0x51f1490
tokens[i] address: 0x51f14e0
token[0]: a
token[1]: boo
==4101== Invalid write of size 8
==4101==    at 0x400F3B: Create_List_Container (search.c:166)
==4101==    by 0x4012D5: main (search.c:234)
==4101==  Address 0x51f1498 is 0 bytes after a block of size 8 alloc'd
==4101==    at 0x4C2B6CD: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==4101==    by 0x400E1A: Create_List_Container (search.c:154)
==4101==    by 0x4012D5: main (search.c:234)
==4101== 
==4101== Invalid read of size 8
==4101==    at 0x400F4F: Create_List_Container (search.c:167)
==4101==    by 0x4012D5: main (search.c:234)
==4101==  Address 0x51f1498 is 0 bytes after a block of size 8 alloc'd
==4101==    at 0x4C2B6CD: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==4101==    by 0x400E1A: Create_List_Container (search.c:154)
==4101==    by 0x4012D5: main (search.c:234)
==4101== 
==4101== Invalid read of size 8
==4101==    at 0x400F6A: Create_List_Container (search.c:161)
==4101==    by 0x4012D5: main (search.c:234)
==4101==  Address 0x51f1498 is 0 bytes after a block of size 8 alloc'd
==4101==    at 0x4C2B6CD: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==4101==    by 0x400E1A: Create_List_Container (search.c:154)
==4101==    by 0x4012D5: main (search.c:234)
==4101== 
token[2]: 1
token[3]: baa
token[4]: 1
token[5]: 

token[6]: baa
token[7]: baa
token[8]: 1
token[9]: 

token[10]: boo
token[11]: boo
token[12]: 1
token[13]: 

token[14]: cat
token[15]: baa
token[16]: 1
token[17]: 

token[18]: dog
token[19]: boo
token[20]: 1
token[21]: 

token[22]: name
token[23]: boo
token[24]: 2
token[25]: baa
token[26]: 1
==4101== Use of uninitialised value of size 8
==4101==    at 0x4EBD146: strtok (strtok.S:172)
==4101==    by 0x400EFA: Create_List_Container (search.c:163)
==4101==    by 0x4012D5: main (search.c:234)
==4101== 
==4101== Conditional jump or move depends on uninitialised value(s)
==4101==    at 0x4EBD149: strtok (strtok.S:173)
==4101==    by 0x400EFA: Create_List_Container (search.c:163)
==4101==    by 0x4012D5: main (search.c:234)
==4101== 
token[27]: 

编辑：仍有错误

因此，我修改了netcoder提供给我的代码，仍然在令牌[I]被malloc’d的地方发生了无效的写入和读取

代码如下：

    char **tokens = malloc(sizeof(char*)+1);
    if (tokens == NULL) {
            // handle malloc error
            printf("Unable to allocate memory. Exiting...\n");
            exit(0);
    }

    // ...
    while (1) {
            if(i == 0) tstring = strtok(contents, "\"(),-> ");
            else tstring = strtok(NULL, "\"(),-> ");

            if(tstring == NULL) break;

            printf("tstring: %s\tlen(tstring): %d\n", tstring, strlen(tstring));

            tokens[i] = malloc(strlen(tstring)+1);
            if (tokens[i] == NULL) {
                    // handle malloc error
                    printf("Unable to allocate memory. Exiting...\n");
                    exit(0);
            }
            printf("tokens address: %p\t*tokens address: %p\n", tokens, tokens[i]);

            char** tmp = realloc(tokens, (i+2)*sizeof(char*));
            if (tmp == NULL) { 
                    // handle realloc error
                    printf("Unable to reallocate memory. Exiting...\n");
                    exit(0);
            }       
            tokens = tmp;

            strcpy(tokens[i], tstring);
            printf("tokens[%d]: %s\n", i, tokens[i]);
            i++;
    }

注意，我在开始时分配了**令牌，而不是像netcoder那样将其保留为空，因为这也给了我一个问题

这里是瓦尔格兰德：

tstring: a  len(tstring): 1
tokens address: 0x51f1490   *tokens address: 0x51f14e0
tokens[0]: a
tstring: boo    len(tstring): 3
==4609== Invalid write of size 8
==4609==    at 0x400F3E: Create_List_Container (search.c:185)
==4609==    by 0x401388: main (search.c:270)
==4609==  Address 0x51f1538 is 0 bytes after a block of size 8 alloc'd
==4609==    at 0x4C2B7B2: realloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==4609==    by 0x400FB1: Create_List_Container (search.c:193)
==4609==    by 0x401388: main (search.c:270)
==4609== 
==4609== Invalid read of size 8
==4609==    at 0x400F4E: Create_List_Container (search.c:186)
==4609==    by 0x401388: main (search.c:270)
==4609==  Address 0x51f1538 is 0 bytes after a block of size 8 alloc'd
==4609==    at 0x4C2B7B2: realloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==4609==    by 0x400FB1: Create_List_Container (search.c:193)
==4609==    by 0x401388: main (search.c:270)
==4609== 
==4609== Invalid read of size 8
==4609==    at 0x400F77: Create_List_Container (search.c:191)
==4609==    by 0x401388: main (search.c:270)
==4609==  Address 0x51f1538 is 0 bytes after a block of size 8 alloc'd
==4609==    at 0x4C2B7B2: realloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==4609==    by 0x400FB1: Create_List_Container (search.c:193)
==4609==    by 0x401388: main (search.c:270)
==4609== 
tokens address: 0x51f1530   *tokens address: 0x51f1580
==4609== Use of uninitialised value of size 8
==4609==    at 0x4C2BFFC: strcpy (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==4609==    by 0x400FF7: Create_List_Container (search.c:201)
==4609==    by 0x401388: main (search.c:270)
==4609== 
==4609== Invalid write of size 1
==4609==    at 0x4C2BFFC: strcpy (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==4609==    by 0x400FF7: Create_List_Container (search.c:201)
==4609==    by 0x401388: main (search.c:270)
==4609==  Address 0x0 is not stack'd, malloc'd or (recently) free'd

固定，它应该是realloc中的（i+2）

对于初学者，您可以：

tokens[i] = (char*)malloc(sizeof(tstring));

首先，不要强制转换

malloc

的返回值。第二，您可能正在寻找的是

strlen

，而不是

sizeof

：

tokens[i] = malloc(strlen(tstring)+1); // +1 for the null terminator

…你至少犯了两次这样的错误

然后，这里是：

char **tokens = (char **)malloc(sizeof(contents));

…同样，强制转换

malloc

的返回值，以及

sizeof（contents）

是任意的，因为您不知道要在其中存储多少元素。对于

realloc

，这是一个很好的例子：

char **tokens = NULL;
// ...
while (...) {
    // ...
    tokens[i] = malloc(strlen(tstring)+1);
    if (tokens[i] == NULL) {
        // handle malloc error
    }

    char** tmp = realloc(tokens, (i+1)*sizeof(char*));
    if (tmp == NULL) {
        // handle realloc error
    }
    tokens = tmp;

    strcpy(tokens[i], tstring);
    i++;
}

还要注意我是如何在循环结束时移动

I++

的，以防止您在应该是

tokens[0]

时访问

tokens[1]

最后，始终检查

malloc

和

realloc

的返回值。对于初学者，您需要：

tokens[i] = (char*)malloc(sizeof(tstring));

首先，不要强制转换

malloc

的返回值。第二，您可能正在寻找的是

strlen

，而不是

sizeof

：

tokens[i] = malloc(strlen(tstring)+1); // +1 for the null terminator

…你至少犯了两次这样的错误

然后，这里是：

char **tokens = (char **)malloc(sizeof(contents));

…同样，强制转换

malloc

的返回值，以及

sizeof（contents）

是任意的，因为您不知道要在其中存储多少元素。对于

realloc

，这是一个很好的例子：

char **tokens = NULL;
// ...
while (...) {
    // ...
    tokens[i] = malloc(strlen(tstring)+1);
    if (tokens[i] == NULL) {
        // handle malloc error
    }

    char** tmp = realloc(tokens, (i+1)*sizeof(char*));
    if (tmp == NULL) {
        // handle realloc error
    }
    tokens = tmp;

    strcpy(tokens[i], tstring);
    i++;
}

还要注意我是如何在循环结束时移动

I++

的，以防止您在应该是

tokens[0]

时访问

tokens[1]

---

最后，始终检查

malloc

和

realloc

的返回值。当您使用malloc时，您传递的是

sizeof（ptr）

，因此它为64位指针分配了8个字节。您希望

malloc（strlen（ptr）+1）

并以null终止它

---

将

sizeof（tstring）

打印到终端，这应该会验证它。

当您malloc时，您传递的是

sizeof（ptr）

，因此它为64位指针分配了8个字节。您希望

malloc（strlen（ptr）+1）

并以null终止它

---

将

sizeof（tstring）

打印到终端，这将验证它。

sizeof

提供变量的大小，而不是字符串的长度。请尝试

strlen

。

char**tokens=（char**）malloc（sizof*tokens*sizeof（contents））顺便问一下：什么是内容？指针还是数组？或typedef类型？请不要强制转换malloc的返回值。
sizeof
提供变量的大小，而不是字符串的长度。请尝试
strlen
。
char**tokens=（char**）malloc（sizof*tokens*sizeof（contents））顺便问一下：什么是内容？指针还是数组？还是typedef类型？请不要强制转换malloc的返回值。您忘记了i+1（在
i+1*sizeof（char*）
中）周围的括号。非常感谢。是代币[i]=对于循环的条件是否为NULL可行？@PeteJodo，
strtok
在找不到更多令牌时返回NULL。您必须先检查返回值，然后再尝试复制它（或对其调用
strlen
），并将其用作循环条件。您忘记了i+1（在
i+1*sizeof（char*）
中）周围的括号。非常感谢。是代币[i]=对于循环的条件是否为NULL可行？@PeteJodo，
strtok
在找不到更多令牌时返回NULL。您必须先检查返回值，然后再尝试复制它（或对其调用
strlen
），并将其用作循环条件。