realloc 错误：已释放对象的校验和不正确

Question

我尝试编写从标准输入读取数据的代码：

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 ));

但是在像这样运行之后： ~# dd if=/dev/zero bs=1024 count=8 | ./测试 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吗？

Answer 1

inputMsgBufCount 应该在您将数据复制到消息缓冲区后增加。您可以在第一次读取时正确执行此操作，但对于其他所有内容，您可以在重新分配后立即增加它。如果您遵循它的值，则在进入循环时它是 1。您重新分配到 2*bufSize，并增加 inputMsgBufCount，使其变为 2。然后读取数据，并将其复制到 msg+2*bufSize代码>.这会破坏你的缓冲区。您应该已复制到 msg+bufSize。只需延迟增加变量，直到复制数据之后。

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