向量弄乱了std :: cout吗？

Question

I'm trying to make a progress bar for a copy of a portion of a disk to another. I am using a progress bar class that deal with printing the progress bar that I found on stack exchange ( https://codereview.stackexchange.com/questions/186535/progress-bar-in-c ) that I have slightly modified to allow more precision (showing the decimal).

However to copy the files i use a vector, and if I put the declaration of the progress bar object after the declaration of my vector I have part of the content of the vector that is showing instead of the progress bar.

here is a code sample that does not work:

vector<char> buff(512);

progress_bar progress{std::cout, 70u, "Formating"};

int fd=open("/dev/sdc1",O_RDONLY);
int fd2=open("/dev/sdb1",O_RDWR);
double NbOfBlocks = 11800.0;
if (fd>0)
{
    for (int i = 0.0; i<NbOfBlocks; i++)
    {
        progress.write(i/NbOfBlocks);
        read(fd,&buff[0],512*i);
        write(fd2,&buff[0],512*i);
    }
}

If I do :

progress_bar progress{std::cout, 70u, "Formating"};

vector<char> buff(512);

int fd=open("/dev/sdc1",O_RDONLY);
int fd2=open("/dev/sdb1",O_RDWR);
double NbOfBlocks = 11800.0;
if (fd>0)
{
    for (int i = 0.0; i<NbOfBlocks; i++)
    {
        progress.write(i/NbOfBlocks);
        read(fd,&buff[0],512*i);
        write(fd2,&buff[0],512*i);
    }
}

Everything works fine.

Any Idea why or how to avoid it ?

Answer 1

read(fd,&buff[0],512*i);

当i> 0时，缓冲区溢出。