Valgrind Segmentation Fault 无效写入大小 8 C

Question

我似乎不明白为什么我的程序在为字符指针分配内存时会导致错误。这是我的代码：

我想要实现的是将数据插入到数组中，稍后可以通过 for 循环读取它以插入到完全不同的链接列表中。但是，此代码似乎引起了问题？请帮忙！

struct fileData {
  char **data;
  size_t used;
  size_t size;
};

void initData(struct fileData *a, size_t initialSize) {
  a->data = malloc(initialSize * sizeof(char));
  if(a->data == NULL) {
        printf("ERROR: Memory allocation failure!\n");
        exit(1);
  }
  a->used = 0;
  a->size = initialSize;
}

void insertLine(struct fileData *a, char *element) {
  if(a->used == a->size) {
        void *pointer;
        a->size *= 2;

        pointer = realloc(a->data, a->size * sizeof(char));
        if(pointer == NULL) {
                freeData(a);

                printf("ERROR: Memory allocation failure!\n");
                exit(1);
        }

        a->data = pointer;
  }

  if(element != NULL) {
        printf("size: %ld", sizeof(element));

        a->data[a->used++] = malloc(sizeof(element));
        if(a->data[a->used++] != NULL)
                strcpy(a->data[a->used++], element);
  } else
        a->data[a->used++] = NULL;
}

void freeData(struct fileData *a) {
  size_t i;
    /* Free all the copies of the strings */
    for (i = 0 ; i < a->used; i++)
        free(a->data[i]);
    free(a->data);
    free(a);
}

Valgrind 的结果：

==8224== Invalid write of size 8
==8224==    at 0x1000015D7: insertLine (ets_utility.c:129)
==8224==    by 0x100001751: readLines (ets_utility.c:149)
==8224==    by 0x1000018F3: load_data (ets_utility.c:199)
==8224==    by 0x1000010FE: main (ets_main.c:44)
==8224==  Address 0x10001d2e8 is 3 bytes after a block of size 5 alloc'd
==8224==    at 0x6B1B: malloc (in /usr/local/Cellar/valgrind/3.10.1/lib/valgrind/vgpreload_memcheck-amd64-darwin.so)
==8224==    by 0x10000146F: initData (ets_utility.c:99)
==8224==    by 0x1000018BF: load_data (ets_utility.c:190)
==8224==    by 0x1000010FE: main (ets_main.c:44)
==8224== 
==8224== Invalid read of size 8
==8224==    at 0x1000015F9: insertLine (ets_utility.c:130)
==8224==    by 0x100001751: readLines (ets_utility.c:149)
==8224==    by 0x1000018F3: load_data (ets_utility.c:199)
==8224==    by 0x1000010FE: main (ets_main.c:44)
==8224==  Address 0x10001d2f0 is 11 bytes after a block of size 5 alloc'd
==8224==    at 0x6B1B: malloc (in /usr/local/Cellar/valgrind/3.10.1/lib/valgrind/vgpreload_memcheck-amd64-darwin.so)
==8224==    by 0x10000146F: initData (ets_utility.c:99)
==8224==    by 0x1000018BF: load_data (ets_utility.c:190)
==8224==    by 0x1000010FE: main (ets_main.c:44)
==8224== 
==8224== Invalid read of size 8
==8224==    at 0x100001625: insertLine (ets_utility.c:131)
==8224==    by 0x100001751: readLines (ets_utility.c:149)
==8224==    by 0x1000018F3: load_data (ets_utility.c:199)
==8224==    by 0x1000010FE: main (ets_main.c:44)
==8224==  Address 0x10001d318 is 24 bytes before a block of size 4,096 free'd
==8224==    at 0x6F57: free (in /usr/local/Cellar/valgrind/3.10.1/lib/valgrind/vgpreload_memcheck-amd64-darwin.so)
==8224==    by 0x13E7D2: fclose (in /usr/lib/system/libsystem_c.dylib)
==8224==    by 0x100001422: readfile (ets_utility.c:86)
==8224==    by 0x1000018C8: load_data (ets_utility.c:193)
==8224==    by 0x1000010FE: main (ets_main.c:44)
==8224== 
==8224== Invalid write of size 1
==8224==    at 0x8C73: memmove$VARIANT$sse3x (in /usr/local/Cellar/valgrind/3.10.1/lib/valgrind/vgpreload_memcheck-amd64-darwin.so)
==8224==    by 0xDDA1B: __strcpy_chk (in /usr/lib/system/libsystem_c.dylib)
==8224==    by 0x100001706: __inline_strcpy_chk (_string.h:94)
==8224==    by 0x100001632: insertLine (ets_utility.c:131)
==8224==    by 0x100001751: readLines (ets_utility.c:149)
==8224==    by 0x1000018F3: load_data (ets_utility.c:199)
==8224==    by 0x1000010FE: main (ets_main.c:44)
==8224==  Address 0x0 is not stack'd, malloc'd or (recently) free'd
==8224== 
==8224== 
==8224== Process terminating with default action of signal 11 (SIGSEGV)
==8224==  Access not within mapped region at address 0x0
==8224==    at 0x8C73: memmove$VARIANT$sse3x (in /usr/local/Cellar/valgrind/3.10.1/lib/valgrind/vgpreload_memcheck-amd64-darwin.so)
==8224==    by 0xDDA1B: __strcpy_chk (in /usr/lib/system/libsystem_c.dylib)
==8224==    by 0x100001706: __inline_strcpy_chk (_string.h:94)
==8224==    by 0x100001632: insertLine (ets_utility.c:131)
==8224==    by 0x100001751: readLines (ets_utility.c:149)
==8224==    by 0x1000018F3: load_data (ets_utility.c:199)
==8224==    by 0x1000010FE: main (ets_main.c:44)

感谢您的帮助...对 C 来说还是新手：/

Answer 1

你有

a->data = malloc(initialSize * sizeof(char));

和

pointer = realloc(a->data, a->size * sizeof(char));

对于第一个malloc，您分配initialSizè字节，而指针通常是四或八字节，因此您只分配了四分之一或八足够的内存。

您需要使用sizeof(char *) 作为大小。