Worst programmer ever?

So I wrote a function to copy a specified number of bytes
from one stream to another:

void vCopyFile(FILE *fIn, FILE *fOut, int iNum) {
    while (iNum--)
        (void)fputc(fgetc(fIn), fOut);
}

I was told the following:
20:34:53 < dinesh> wow
20:35:00 < dinesh> probably one of the worst function i ever saw

So I changed it to this:

void vCopyFile(FILE *fIn, FILE *fOut, int iNum) {
    char *cBuf = (char*)malloc(iNum);
    int iRead;

    iRead = fread(cBuf, 1, iNum, fIn);
    fwrite(cBuf, 1, iRead, fOut);
}

Both functions work on Linux but seem to skip bytes when
crosscompiled with mingw32-gcc or visual studio.

What am I doing wrong?

unsigned char buffer[1048576];
fail
int bytes_read = 0;
fread returns size_t which is an object of unsigned type.
and why do you set it to 0?

        size_t bytes;
        while(bytes = fread(buffer, 1, sizeof(buffer), stdin)) {
            if(feof(stdin)) break;
            fwrite(buffer, bytes_read, 1, stdout);
        }