Valgrind 给出错误：“条件跳转或移动取决于未初始化的值”答案

【问题标题】：Valgrind giving error: "Conditional jump or move depends on uninitialised value(s)"Valgrind 给出错误：“条件跳转或移动取决于未初始化的值”
【发布时间】：2014-03-23 23:49:16
【问题描述】：

我很确定我知道这个错误意味着什么。这很不言自明。但我不明白为什么。特别是因为错误仅指向第 59 行和第 61 行。就像函数 printDictionary 和 menu 一样。我不明白为什么它会在loadDictionary 上工作，它采用相同的变量作为参数。有什么建议吗？

int main(int argc, char* argv[])
{
    char **wordArray;   /* declare the dynamic array of strings, not yet allocated.*/

    int capacity = INITIAL_ARRAY_MAX;
    int wordCount = 0;

    if (argc != 3)
    {
        fprintf(stderr,"Usage: %s inputfile outputfile\n", argv[0]);
        return 1;
    }

    if (loadDictionary(argv[1], &wordArray, &wordCount, &capacity) != 0)
    {
        fprintf(stderr,"    loadDictionary failed! Program terminating...\n");
        return 1; /* already in main() so exit unneccesary.*/
    }

    printf("\n  Finished loading %d words from dictionary.\n", wordCount);

    printDictionary(wordArray, wordCount);   /* Line 59 */

    menu(&wordArray, &wordCount, argv[2]);   /* Line 61 */

    return 0;
}

这是我的 loadDictionary 函数。它确实初始化了数组！此外，我只是在 loadDicitonary 之前尝试了 addign 函数，并且在它之前将数组作为参数的任何函数都有效。所以问题显然出在 loadDictionary 上。

int loadDictionary(char *inputFileName, char ***array, int *count, int *capacity)
{
    FILE *inputFile;
    char word[WORD_LENGTH];

    if ((inputFile = fopen(inputFileName, "r")) == NULL)
    {
        fprintf(stderr,"Error opening input file, %s\n", inputFileName);
    return -1;
    }

    *array = (char **)malloc(*capacity * sizeof(char*));
    if (*array == NULL)
    {
        fprintf(stderr, "Malloc of array in loadDictionary failed!\n");
        return -1;
    }

    printf("Reading file %s (each . is 5000 words read)\n", inputFileName);

    *count = 0;
    while (fscanf(inputFile, "%s", word) == 1)
    {
        if (*count >= *capacity)
        {
            /*makes new array of double size with contents of original array.*/
            if (doubleArraySize(array, *count, capacity) != 0){
                fprintf(stderr, "Doubling array failed!\n");
            }
        }
        if (insertWord(*array, count, word) != 0)
        {
            fprintf(stderr,"    Insert returned an error!\n");
            fclose(inputFile);
            return 1;
        }

        if (*count % 5000 == 0)
        {
             printf(".");
             fflush(stdout);
        }
    }

    fclose(inputFile);

    return 0;
}

Valgrind 日志。

==6107== Memcheck, a memory error detector
==6107== Copyright (C) 2002-2011, and GNU GPL'd, by Julian Seward et al.
==6107== Using Valgrind-3.7.0 and LibVEX; rerun with -h for copyright info
==6107== Command: ./lab2 105-words.txt output.txt
==6107== Parent PID: 3994
==6107==
==6107== Conditional jump or move depends on uninitialised value(s)
==6107==    at 0x4089E29: vfprintf (vfprintf.c:1630)
==6107==    by 0x4091EFE: printf (printf.c:35)
==6107==    by 0x804882F: main (lab2.c:59)
==6107==
==6107== Conditional jump or move depends on uninitialised value(s)
==6107==    at 0x4089E29: vfprintf (vfprintf.c:1630)
==6107==    by 0x4091EBE: fprintf (fprintf.c:33)
==6107==    by 0x8048F49: menu (lab2.c:271)
==6107==    by 0x804884F: main (lab2.c:61)
==6107==
==6107==
==6107== HEAP SUMMARY:
==6107==    in use at exit: 0 bytes in 0 blocks
==6107==   total heap usage: 110 allocs, 110 frees, 3,197 bytes allocated
==6107==
==6107== All heap blocks were freed -- no leaks are possible
==6107==
==6107== For counts of detected and suppressed errors, rerun with: -v
==6107== Use --track-origins=yes to see where uninitialised values come from
==6107== ERROR SUMMARY: 210 errors from 2 contexts (suppressed: 0 from 0)

【问题讨论】：

loadDictionary 是如何工作的？我的猜测是有一个代码路径返回0，但没有设置wordArray。
第 59 行和第 61 行分别是哪几行？
第 59 行 -> printDictionary(wordArray, wordCount);第 61 行 -> 菜单(&wordArray, &wordCount, argv[2]);
我没有看到有条件的跳转或移动这些调用中的任何一个。你能发布完整、准确的错误信息吗？
错误中的行号与源代码不匹配。请重新编译并再次运行valgrind。（另外，您还没有将源代码包含到 menu() 函数中。）

标签： c pointers valgrind

【解决方案1】：

上面的Valgrind 消息表明在您的程序中某处未初始化的变量已被使用。

要查看程序中未初始化数据来源的信息，请使用以下选项：

--track-origins=yes

这将帮助您找出程序中未初始化值错误的根本原因。

【讨论】：