Once again encountered the limits of 32 bit Linux, manely 2GB files.  For an upload, it seems the connection is broken & the browser resends the file when it hits the limit.  Java had 64 bit file sizes from the beginning but 32 bit C was never upgraded.  You still have to provide good old -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 flags on the 32 bit raspberry pi.  Helas %ld for printf is no more.  You now have to use %lld to print 64 bit ints.

Also, long as a function argument didn't work on the 32 bit pi.  You have to use int64_t everywhere to get reliable results.

There was another corner case in decode_url where it wasn't supposed to convert + to "   ".  According to https://docs.oracle.com/javase/8/docs/api/java/net/URLDecoder.html  The plus sign "+" is converted into a space character "   " .

But this turned out to break URL decoding.