c - Valgrind大喊一个未初始化的字节

Valgrind将我抛出此错误:

==11204== Syscall param write(buf) points to uninitialised byte(s)
==11204==    at 0x4109033: write (in /lib/libc-2.13.so)
==11204==    by 0x8049654: main (mmboxman.c:289)
==11204==  Address 0xbe92f861 is on thread 1's stack
==11204==

有什么问题？我找不到它在喊什么未初始化字节。
这是犯罪的代码行(提到的289行是调用函数lockUp的那一行):

Request request;
Response response;

fillRequest(&request, MANADDUSER, getpid(), argument1, NULL, NULL, 0, 0);
lockUp(&request, &response, NULL);

这里的函数原型(prototype)和结构声明:

void fillRequest(Request *request, char code, pid_t pid, char *name1, char *name2, char   *object, int id, size_t size)
{
    int k;

    request->code = code;
    request->pid = getpid();

    if(name1)    for(k=0; k<strlen(name1)+1; k++)   request->name1[k] = name1[k];
    else         request->name1[0] = '\0';

    if(name2)    for(k=0; k<strlen(name2)+1; k++)   request->name2[k] = name2[k];
    else         request->name2[0] = '\0';

    if(object)   for(k=0; k<strlen(name2)+1; k++)   request->name2[k] = name2[k];
    else         request->object[0] = '\0';

    request->id    = id;
    request->size = size;
}

void lockUp(Request *request, Response *response, void **buffer)
{
    int fifofrom, fifoto, lock;     /* file descriptor delle fifo e del lock */

    /* locko per l'accesso alle FIFO */
    if((lock = open(LOCK, O_RDONLY)) == -1)   logMmboxman("error in opening LOCK\n", 1);
    else                                      logMmboxman("opened LOCK\n", 0);

    if(flock(lock, LOCK_EX) == -1)            logMmboxman("error in acquiring LOCK\n", 1);
    else                                              logMmboxman("acquired LOCK\n", 0);

    /* apro la fifoto e scrivo la mia richiesta */
    if((fifoto = open(FIFOTOMMBOXD, O_WRONLY)) == -1)   logMmboxman("error in opening FIFOTO\n", 1);
    else                                                logMmboxman("opened FIFOTO\n", 0);

    if((write(fifoto, request, sizeof(Request))) != sizeof(Request))   logMmboxman("error in writing FIFOTO\n", 1);
    else                                                               logMmboxman("written on FIFOTO\n", 0);
    close(fifoto);

    /* rimango in attesa della risposta da mmboxd sulla fifofrom */
    if((fifofrom = open(FIFOFROMMMBOXD, O_RDONLY)) == -1)   logMmboxman("error in opening FIFOFROM\n", 1);
    else                                                    logMmboxman("opened FIFOFROM\n", 0);

    if((read(fifofrom, response, sizeof(Response))) != sizeof(Response))   logMmboxman("error in reading FIFOFROM\n", 1);
    else                                                                   logMmboxman("read from FIFOFROM\n", 0);
    close(fifofrom);

    /* se mi deve comunicare un buffer riapro la fifo e lo leggo */
    if(response->size)
    {
            if((fifofrom = open(FIFOFROMMMBOXD, O_RDONLY)) == -1)   logMmboxman("error in opening FIFOFROM again for the buffer\n", 1);
            else                                                    logMmboxman("opened FIFOFROM again for the buffer\n", 0);

            *buffer = (void*)malloc(response->size);

            if(read(fifofrom, *buffer, response->size) != response->size)   logMmboxman("error in reading FIFOFROM again for the buffer\n", 1);
            else                                                            logMmboxman("read from FIFOFROM again for the buffer\n", 0);
            close(fifofrom);
    }

    /* letta la risposta rilascio il lock */
    if(flock(lock, LOCK_UN) == -1)            logMmboxman("error in releasing LOCK\n", 1);
    else                                      logMmboxman("released LOCK\n", 0);

    return;
}

typedef struct
{
    char code;
    pid_t pid;
    char name1[41];
    char name2[41];
    char object[101];
    int id;
    size_t size;
} Request;

typedef struct
{
    char result;
    int num;
    int num2;
    size_t size;
} Response;

最佳答案

您的Request结构具有数组name1，name2等，其中包含以空字符结尾的字符串。当您填写它们时，您不会写空终止符。稍后，当您将结构写入文件时，valgrind会抱怨，因为这些字节未初始化。可能还有其他未初始化的字节(例如，编译器插入的填充)。

除了一个小的安全性问题外，这不一定是一个问题:可能包含敏感信息的以前的内存内容将被写入文件。

您可以在填充结构域之前将其设置为0，以避免此错误。

关于c - Valgrind大喊一个未初始化的字节，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/5844242/