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我正在尝试编写一个函数来搜索所有出现的模式并返回文件中与模式匹配的偏移量数组。我想使用 realloc 来动态增长我返回的数组，但是我得到一个 sSYSMALLOC 断言错误。有时，如果我使用不同的搜索模式，我可能会收到无效的下一个尺寸错误。我的机器上还没有 valgrind（需要使用调试标志重建 glibc）。这似乎是一个简单的问题，我只触摸这个指针两次 - 一次声明它并将其设置为 NULL，然后再次重新分配以增长它。我知道 sizeof(char) 是 1，在我的 realloc 语句中没有用。

这是有问题的函数的代码。

unsigned long long* searchBytes(FILE* fp, char* byteString, char* searchType, unsigned   long long fileSize)
{
if (fp == NULL)
    return NULL;

unsigned long long* foundBytes = NULL;
long numBytes = 0;

// make some memory for the array of found bytes
if (strcmp(searchType, "ascii") == 0)
{
    numBytes = strlen(byteString);
    //foundBytes = realloc(NULL, numBytes * sizeof(char));
}
else
{
    // TODO strip the spaces from the string and handle hex searches
    printf("hex-search not implemented yet.\n");
    return NULL;
}

// loop over all the bytes in the file looking for this ascii pattern
unsigned long long currentOffset = 0;
unsigned long long origOffset = 0;
unsigned long long m = 0;
foundWords = 0;
char* possibleWord = malloc(numBytes * sizeof(char));

do
{
    fseek(fp, currentOffset, SEEK_SET);
    unsigned long long i;
    int n = 0;
    int failed = 0;
    origOffset = currentOffset;

    for(i=currentOffset; i<currentOffset+numBytes; i++)
    {
        possibleWord[n] = fgetc(fp);
        n++;
    }
    //printf("possibleWord: %s\n", possibleWord);

    // is this our word? use strstr just in case
    char* found = strstr((const char*) byteString, (const char*) possibleWord);
    if (found)
    {
        foundWords++;
        // make a bigger spot for it
        printf("allocating %ld bytes to add word %d to list...\n", (numBytes*foundWords) * sizeof(char), foundWords);
        unsigned long long* p = realloc(foundBytes, (numBytes*foundWords) * sizeof(char));
        if (p)
        {
            foundBytes = p;

            for (i = origOffset; i<origOffset+numBytes; i++)
            {
                foundBytes[m] = i;
                //printf("added offset %llu to foundBytes[%llu]\n", i, m);
                m++;
            }

        }
        else
        {
            return NULL;
        }

    }
    else
    {
        failed = 1;
    }

    if (failed == 0)
    {
        currentOffset += numBytes;
        //printf("Yay! moving forward %ld bytes.\n", numBytes);
    }
    else
    {
        currentOffset++;
    }   
}
while (currentOffset < fileSize);

if (foundWords > 0)
{
    //printf("returning foundBytes!\n");

    //unsigned long long z;
    //for (z=0; z<foundWords*numBytes; z++)
    //  printf("%llu\n", foundBytes[z]);
    //printf("...\n");
    return foundBytes;
}
//printf("returning NULL\n");
return NULL;
}

当使用“root”作为搜索模式在 /etc/passwd 上运行时：

allocating 4 bytes to add word 1 to list...
allocating 8 bytes to add word 2 to list...
*** glibc detected *** ./chex3: realloc(): invalid next size: 0x0000000001a59270 ***

或在 /etc/passwd 上使用“daemon”作为搜索模式：

allocating 6 bytes to add word 1 to list...
allocating 12 bytes to add word 2 to list...
chex3: malloc.c:2451: sYSMALLOc: Assertion `(old_top == (((mbinptr) (((char *) &((av)->bins[((1) - 1) * 2])) - __builtin_offsetof (struct malloc_chunk, fd)))) && old_size == 0) || ((unsigned long) (old_size) >= (unsigned long)((((__builtin_offsetof (struct malloc_chunk, fd_nextsize))+((2 * (sizeof(size_t))) - 1)) & ~((2 * (sizeof(size_t))) - 1))) && ((old_top)->size & 0x1) && ((unsigned long)old_end & pagemask) == 0)' failed.

有人可以看看这个，看看它看起来是否正常？谢谢！我是一个试图学习的菜鸟:)

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1 回答 1

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解决方案是使用 foundBytes 对 p 进行 decalure，然后将 realloc 行更改为：

p = realloc(foundBytes, (numBytes*foundWords) * sizeof(*p));

我必须承认我真的不明白为什么这是必要的，似乎我以这种方式分配了很多。（对于 3 个字符的搜索模式，每次添加 24 个字节而不是 3 个字节）

于 2012-12-18T16:57:22.043 回答