Question

我尝试编写从stdin读取数据的代码：

size_t bufSize = 1024;
unsigned char *msg = NULL;
size_t msgBytes = 0;
size_t inputMsgBufCount = 0;
unsigned char inputBuffer[bufSize];
size_t bytesRead = 0;
unsigned char *tmp = NULL;

if ((msg = (unsigned char *)malloc(sizeof(unsigned char) * bufSize)) == NULL)
    exit(EXIT_FAILURE);
bytesRead = fread(msg, sizeof(unsigned char) * bufSize, 1, stdin);
inputMsgBufCount++;

while (bytesRead) {
    printf("iteration: %lu\n", inputMsgBufCount);
    if ( (tmp = (unsigned char *)realloc(msg, (inputMsgBufCount * bufSize) + bufSize)) != NULL ) {
         printf("reallocated\n");
        msg = tmp;
        inputMsgBufCount++;
    }
    else {
        printf("Ran out of memory\n");
        free(msg);
    }
    bytesRead = fread(inputBuffer, sizeof(unsigned char) * bufSize, 1, stdin);
    memmove((msg + (inputMsgBufCount * bufSize)), inputBuffer, bufSize);
}

free(msg);

msgBytes = (inputMsgBufCount * bufSize);

gettimeofday(&end, NULL);
printf("%10.6lf [MB/s]\n", (msgBytes / (1<<20)) / ( (end.tv_sec - start.tv_sec) + (end.tv_usec - start.tv_usec) * 1.0e-6f ));

但是这样运行之后： 〜＃dd if = / dev / zero bs = 1024 count = 8 | ./test 我有这个错误：

iteration: 1
reallocated
iteration: 2
reallocated
iteration: 3
reallocated
iteration: 4
reallocated
iteration: 5
reallocated
iteration: 6
reallocated
iteration: 7
test(11450) malloc: *** error for object 0x100804008: incorrect checksum for freed object - object was probably modified after being freed.
*** set a breakpoint in malloc_error_break to debug
Abort trap

任何人都可以帮助我。

Answer 1

在中复制msg缓冲区中的数据后，

inputMsgBufCount应该递增。你在第一次阅读时就做对了，但对于其他一切，你在重新分配后立即增加它。如果您遵循它的值，则在您进入循环时它为1。您重新分配到2*bufSize，并增加inputMsgBufCount，这使其成为2.然后您阅读数据，并将其复制到msg+2*bufSize。这会破坏你的缓冲区。您应该已复制到msg+bufSize。只需延迟递增变量，直到复制数据为止。

另一方面，您可以安全地使用memcpy()复制数据。 msg和inputBuffer永远不会重叠。实际上你应该完全摆脱inputBuffer，并在正确的偏移处直接读到msg。

realloc错误：释放对象的校验和不正确

1 个答案: