Question

This is a part of my program:

  while((total_bytes_read != fsize) && ((nread = read(f_sockd, filebuffer, fsize_tmp)) > 0)){
    if(write(fd, filebuffer, nread) != nread){
      perror("write RETR");
      onexit(f_sockd, 0, 0, 1);
    }
    total_bytes_read += nread;
    fsize_tmp -= nread;
  }

where total_bytes_read, fsize, nread are declared as uint32_t.
On a 64 bit machine there’s no problem, it compiles and run very well (this part of code has to receive a file).
The problem is when i compile on a 32bit machine because i got this error:
warning: comparison of integers of different signs: 'ssize_t' (aka 'int') and 'uint32_t' (aka 'unsigned int') [-Wsign-compare] if(write(fd, filebuffer, nread) != nread){
I don’t know how to solve this problem because if i change if(write(fd, filebuffer, nread) != nread){ to if(nread != (uint32_t)write(fd, filebuffer, nread)){ the program doesn’t receive the file anymore but it print (part of) the file content to stdout.
Why i got this strange behaviour and how can i solve this thing?

Answer 1

Just use the right types. The standard says:

ssize_t read(int fildes, void *buf, size_t nbyte);
^^^^^^^                             ^^^^^^

So that’s what you should use. Not int, not uint64_t, not unsigned long long etc.