制作一個程式，列出目錄中的檔案并對輸出進行排序

我opendir(.)用來打開我想要讀取的目錄的路徑。然后我使用readdir回圈來遍歷當前目錄中的所有檔案和目錄。然后我有一個char**串列來存盤 readdir 的內容。然后我進行排序**list以按字典順序排列。僅當我有一個長度超過 63 個字符的檔案時，我在對輸出進行排序時不斷收到溢位錯誤。為什么會這樣，我該如何解決？

void ls_short() {
    char **list = NULL;
    int count = 0;
    DIR  *dir;
    struct dirent *rd;
    dir = opendir(".");
    // check to make sure that we can open the directory
    if(dir == NULL){
        perror("Not able to open The current directory.");
        exit(EXIT_FAILURE);
    }
    
    while((rd = readdir(dir)) != NULL){
        list = realloc(list, (count 1)*sizeof(*list));
        list[count] = rd ->d_name;
          count;
        printf("%s\n",rd ->d_name);
    }
    printf("here we will print the list\n");
    for (int i = 0; i < count;i  ){
        printf("%s\n",list[i]);
    }
    printf("Now we print the list in order and also get rid of . and .. directory\n");
    list = realloc(list, (count 1)*sizeof(*list));
    list[count] = "";
    for (int i = 0; i < count - 1; i  ){
        for (int j = 0; j < count - i - 1; j  ){
            if (strcasecmp(list[j], list[j   1]) > 0) {
                    char* temp;
                    temp = (char*)calloc(count, sizeof(char)*256);
                    strcpy(temp, list[j]);
                    strcpy(list[j], list[j   1]);
                    strcpy(list[j   1], temp);
                    free(temp);
            }
        }
    }
    for (int i = 2; i < count;i  ){
        printf("%s\n",list[i]);
    }
    closedir(dir);
}

這是我得到的錯誤：

=================================================================
==43335==ERROR: AddressSanitizer: strcpy-param-overlap: memory ranges [0x6250000001fd,0x625000000220) and [0x62500000021d, 0x625000000240) overlap
    #0 0x103ef03ef in wrap_strcpy 0xaf (libclang_rt.asan_osx_dynamic.dylib:x86_64h 0x433ef)
    #1 0x103e9aa5d in ls_short ls.c:61
    #2 0x103e9a5c4 in main ls.c:16
    #3 0x7fff20379620 in start 0x0 (libdyld.dylib:x86_64 0x15620)

0x6250000001fd is located 253 bytes inside of 8192-byte region [0x625000000100,0x625000002100)
allocated by thread T0 here:
    #0 0x103ef54c0 in wrap_malloc 0xa0 (libclang_rt.asan_osx_dynamic.dylib:x86_64h 0x484c0)
    #1 0x7fff2025b0fe in _readdir_unlocked$INODE64 0x6d (libsystem_c.dylib:x86_64 0x2a0fe)
    #2 0x7fff2025b227 in readdir$INODE64 0x22 (libsystem_c.dylib:x86_64 0x2a227)
    #3 0x103e9a6ad in ls_short ls.c:42
    #4 0x103e9a5c4 in main ls.c:16
    #5 0x7fff20379620 in start 0x0 (libdyld.dylib:x86_64 0x15620)

0x62500000021d is located 285 bytes inside of 8192-byte region [0x625000000100,0x625000002100)
allocated by thread T0 here:
    #0 0x103ef54c0 in wrap_malloc 0xa0 (libclang_rt.asan_osx_dynamic.dylib:x86_64h 0x484c0)
    #1 0x7fff2025b0fe in _readdir_unlocked$INODE64 0x6d (libsystem_c.dylib:x86_64 0x2a0fe)
    #2 0x7fff2025b227 in readdir$INODE64 0x22 (libsystem_c.dylib:x86_64 0x2a227)
    #3 0x103e9a6ad in ls_short ls.c:42
    #4 0x103e9a5c4 in main ls.c:16
    #5 0x7fff20379620 in start 0x0 (libdyld.dylib:x86_64 0x15620)

SUMMARY: AddressSanitizer: strcpy-param-overlap (libclang_rt.asan_osx_dynamic.dylib:x86_64h 0x433ef) in wrap_strcpy 0xaf
==43335==ABORTING
Abort trap: 6

uj5u.com熱心網友回復：

readdir()有一個靜態緩沖區rd->d_name，每次呼叫時都會重用它，因此所有list元素都指向同一個字串。

當您將字串分配給陣列時，您應該制作它們的副本。

list[count] = strdup(rd->d_name);

并且在排序時，不要在字串之間復制名稱，只需交換指標即可。

            if (strcasecmp(list[j], list[j   1]) > 0) {
                char* temp;
                temp = list[j];
                list[j] = list[j 1];
                list[j 1] = temp;
            }

uj5u.com熱心網友回復：

    while((rd = readdir(dir)) != NULL){
        list = realloc(list, (count 1)*sizeof(*list));
        list[count] = rd ->d_name;
          count;
        printf("%s\n",rd ->d_name);
    }

您無處分配記憶體來保存您添加到串列中的字串。您分配記憶體來保存指向它的指標，僅此而已。

您需要更改list[count] = rd ->d_name;為：

    list[count] = malloc(256);
    strcpy(list[count], rd->d_name);

此外，排序時不需要為字串分配新記憶體。如果您已經為需要存盤的每個字串分配了記憶體（您必須這樣做或者您的串列已經損壞），為什么更改順序需要分配新的記憶體來保存字串？

標籤：C 排序 malloc ls

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