Question

我从valgrind那里得到了一些神秘的未初始化的价值观信息，而且这个价值来自于坏的价值所在。不要有人知道哪里有问题？非常感谢有记忆错误，我一直在这里：

==26075== Memcheck, a memory error detector
==26075== Copyright (C) 2002-2011, and GNU GPL'd, by Julian Seward et al.
==26075== Using Valgrind-3.7.0 and LibVEX; rerun with -h for copyright info
==26075== Command: ./main
==26075== 
==26075== Conditional jump or move depends on uninitialised value(s)
==26075==    at 0x4C2A020: strcmp (mc_replace_strmem.c:711)
==26075==    by 0x400CF6: stringcmp (main.c:121)
==26075==    by 0x4E64C69: msort_with_tmp (msort.c:84)
==26075==    by 0x4E6503B: qsort_r (msort.c:298)
==26075==    by 0x400930: main (main.c:42)
==26075== 
==26075== Conditional jump or move depends on uninitialised value(s)
==26075==    at 0x4C2A024: strcmp (mc_replace_strmem.c:711)
==26075==    by 0x400CF6: stringcmp (main.c:121)
==26075==    by 0x4E64C69: msort_with_tmp (msort.c:84)
==26075==    by 0x4E6503B: qsort_r (msort.c:298)
==26075==    by 0x400930: main (main.c:42)
==26075== 
==26075== 
==26075== HEAP SUMMARY:
==26075==     in use at exit: 0 bytes in 0 blocks
==26075==   total heap usage: 4 allocs, 4 frees, 31 bytes allocated
==26075== 
==26075== All heap blocks were freed -- no leaks are possible
==26075== 
==26075== For counts of detected and suppressed errors, rerun with: -v
==26075== Use --track-origins=yes to see where uninitialised values come from
==26075== ERROR SUMMARY: 2 errors from 2 contexts (suppressed: 4 from 4)

有我的代码：

    #include <stdio.h>
#include <string.h>
#include <malloc.h>
#include <stdlib.h>

char *input;
int row = 0;


int stringcmp(const void *a, const void *b);

void permute(int n, int fix, char **arr);

int factorial(int n);

void swapSort(char array[], int left, int right);

void quick_sort(char *array, int left, int right);

void free2DArray(char **array, int row);

int main() {
    input = (char *) malloc(8 + 1 * sizeof(char));
    fgets(input, 9, stdin);
    int n = strlen(input);
    if (input[n - 1] == '\n') {
        n--;
        input[n] = '\0';
    }
    int f = factorial(n);
    printf("Length of string: %d\n", n);
    printf("Input string: \"%s\"\n", input);
    quick_sort(input, 0, n);
    printf("Sorted: \"%s\"\n", input);
    printf("Number of permutations: %d\n", f);
    char **arrOfPermutations = (char **) malloc(factorial(n) * sizeof(char *));
    for (int i = 0; i < factorial(n); i++) {
        arrOfPermutations[i] = (char *) malloc((n + 1) * sizeof(char));
    }

    permute(n, n, arrOfPermutations);
    qsort(arrOfPermutations, f, sizeof(char *), stringcmp);
    for (int i = 0; i < f; i++) {
        printf("\"");
        for (int j = 0; j < n; j++) {
            printf("%c", arrOfPermutations[i][j]);
        }
        printf("\"\n");
    }
    free2DArray(arrOfPermutations, f);
    free(input);

    return 0;
}


void free2DArray(char **array, int row) {
    for (row -= 1; row >= 0; row--)
        free(array[row]);
    free(array);
}

void permute(int n, int fix, char **arr) {
    int i, j;
    char temp;
    if (n == 0) {
        for (j = fix - 1, i = 0; j >= 0; j--, i++) {
            arr[row][i] = input[j];
        }
        row++;
    }
    for (i = 0; i < n; i++) {
        temp = input[i];
        for (j = i + 1; j < n; j++) {
            input[j - 1] = input[j];
        }
        input[n - 1] = temp;

        permute(n - 1, fix, arr);

        for (j = n - 1; j > i; j--) {
            input[j] = input[j - 1];
        }
        input[i] = temp;
    }
}

int factorial(int n) {
    if (n == 1) return 1;
    return n * factorial(n - 1);

}


void quick_sort(char *array, int left, int right) {
    if (left < right) {
        int boundary = left;
        for (int i = left + 1; i < right; i++) {
            if (array[i] < array[left]) {
                swapSort(array, i, ++boundary);
            }
        }
        swapSort(array, left, boundary);
        quick_sort(array, left, boundary);
        quick_sort(array, boundary + 1, right);
    }

}

void swapSort(char array[], int left, int right) {
    char tmp = array[right];
    array[right] = array[left];

    array[left] = tmp;
}


int stringcmp(const void *a, const void *b) {
    const char **ia = (const char **) a;
    const char **ib = (const char **) b;
    return strcmp(*ia, *ib);
}

Answer 1

除了少数其他较小的问题你正确地反向复制字符串，但最后没有附加零字节。

if (n == 0) {
    for (j = fix - 1, i = 0; j >= 0; j--, i++) { <<-- The problem is in this line
        arr[row][i] = input[j];
    }
    row++;
}

你不能反复复制行尾标记，因为它应该保留在最后，所以你必须在之后添加它：

if (n == 0) {
    for (j = fix - 1, i = 0; j >= 0; j--, i++) { 
        arr[row][i] = input[j];
    }
    arr[row][fix]=0; <<-- the fix
    row++;
}

Valgrind-未初始化的值消息

1 个答案: