valgrind報告錯誤，並且在使用realloc時肯定丟失（）

Question

以下是兩個函數，其中第一個函數試圖根據計數值爲指針數組分配內存並隨後重新分配內存。

第二個函數試圖將最後一個字符串向前連接到指針數組中的第一個字符串。

程序需要將字符串和模式的數量作爲命令行參數進行匹配，並僅在輸入字符串中找到匹配模式時調用第一個函數。

20 char **allocate_array_of_ptrs(char **str_array, /* pointer to the array of pointers */ 
21      char *str,    /* pointer to the input string */ 
22      int count)    /* count of matched strings */ 
23 { 
24   char **temp = NULL;   /*  temporary pointer to realloc memory */ 
25 
26   /* realloc based on count value */ 
27   temp = (char **)realloc(str_array, count * sizeof(char *)); 
28 
29   int str_len = strlen(str); 
30 
31   /* if realloc is successful */ 
32   if (NULL != temp) 
33   { 
34     str_array = temp; 
35 
36     /* alloc memory for the string to be stored */ 
37     temp[count - 1] = (char *)calloc((str_len + 1), sizeof(char)); 
38     strcpy(temp[count - 1], str); 
39   } 
40 
41   return str_array; 
42 } 
43 
44 char **dmm_str_cat(char **str_array,   /* pointer to the array of pointers */ 
45    int count)      /* count of matched strings */ 
46 { 
47   int i;           /* iterator */ 
48   int total_str_len = 0;  /* total length when all strings put together */ 
49   int str_len_of_first;  /* string length of first string in the array */ 
50 
51   if (count > 1) 
52   { 
53     str_len_of_first = strlen(str_array[0]); 
54 
55     for (i = 0; i < count; i++) 
56     { 
57       total_str_len += strlen(str_array[i]); 
58     } 
59     total_str_len += 1; 
60 
61    /* realloc memory to accomodate all matched strings onto first string */ 
62   str_array[0] = (char *)realloc(str_array[0], total_str_len * sizeof(char)); 
63 
64     /* clearing the new allocated bytes */ 
65     for (i = (str_len_of_first + 1); i < total_str_len; i++) 
66     { 
67       str_array[0][i] = '\0'; 
68     } 
69 
70     /* concatenate from the last string onwards onto first string */ 
71     for (i = count - 1; i > 0; i--) 
72     { 
73       strcat(str_array[0], str_array[i]); 
74     } 
75   } 
76 
77   return str_array; 
78 } 

的問題是，當代碼下的valgrind運行，它報告下面的消息時出3串，2個字符串不匹配模式「EL」。其他組合報告了類似的錯誤。

 Enter string 1 : matter 

     Enter string 2 : matter 

     Enter string 3 : jello 

     Count of strings having matching pattern 'el' : 1 
     The matching strings are : 
       jello 
==6244== Invalid read of size 8 
==6244== at 0x400A74: main (dmm_main.c:86) 
==6244== Address 0x4C33038 is 0 bytes after a block of size 8 alloc'd 
==6244== at 0x4A05809: malloc (vg_replace_malloc.c:149) 
==6244== by 0x4A05883: realloc (vg_replace_malloc.c:306) 
==6244== by 0x400AE9: allocate_array_of_ptrs (dmm_functions.c:27) 
==6244== by 0x4009B6: main (dmm_main.c:64) 
==6244== 
==6244== Invalid write of size 8 
==6244== at 0x400A89: main (dmm_main.c:87) 
==6244== Address 0x4C33038 is 0 bytes after a block of size 8 alloc'd 
==6244== at 0x4A05809: malloc (vg_replace_malloc.c:149) 
==6244== by 0x4A05883: realloc (vg_replace_malloc.c:306) 
==6244== by 0x400AE9: allocate_array_of_ptrs (dmm_functions.c:27) 
==6244== by 0x4009B6: main (dmm_main.c:64) 
     The concatenated string is : jello==6244== 
==6244== ERROR SUMMARY: 2 errors from 2 contexts (suppressed: 4 from 1) 
==6244== malloc/free: in use at exit: 0 bytes in 0 blocks. 
==6244== malloc/free: 2 allocs, 2 frees, 14 bytes allocated. 
==6244== For counts of detected errors, rerun with: -v 
==6244== All heap blocks were freed -- no leaks are possible. 

但是，當有匹配的模式，而一個不匹配的兩個字符串，則有由Valgrind的報告沒有錯誤/泄漏。當所有字符串匹配模式時，肯定會丟失報告。

Answer 1

考慮到，你已經無效讀取然後再無效寫帳戶，我敢打賭，str_array傳遞給allocate_array_of_ptrs沒有正確initialized-

實際上，消息0 bytes after a block of size 8 alloc'd讓我覺得你overpassing數組大小，但我不能100％肯定沒有main.c代碼。