[php-src] Issue #11753: stream_copy_to_stream returns false when data copied is less than $maxlength

Issue: https://github.com/php/php-src/issues/11753 Author: stevesutton-hds ### Description The following code: ```php <?php $streaminput = popen("my_command", "r"); // Some command which has generated output that sometimes has less than the 10000 read size bytes of data (if you care, I was actually calling postgres's pg_dump) $streamoutput = popen("another_command", "w"); // I was actually using input pipe (i.e. stdin) of command started with proc_open() here (actually it was gzip, and I used proc_open so that I could read stdout her too), but AFAIK, that's just a stream to stdin as is the case in this example) $expectedPos = 0; while (!feof($streaminput)) { $copied = stream_copy_to_stream($streaminput, $streamoutput, 10000); $expectedPos += $copied; // if ($copied === false) { echo "\nCopied is false!"; // if ($copied === 0) { echo "\nCopied is false!"; // This message never printed if ($copied == 0) { // Note: I later discovered that the unexpected false return caused the branch to execute because of == instead of ===, even though the stream position had advanced. echo "."; sleep 1; continue; else { echo "\nCopied $copied, Expected position $expectedPos, actual position " . ftell($streaminput); } } ``` Resulted in this output: ``` Copied 10000, Expected position 10000, actual position 10000 Copied 10000, Expected position 20000, actual position 20000 Copied 10000, Expected position 30000, actual position 30000. Copied 10000, Expected position 48192, actual position 40000 Copied 10000, Expected position 58192, actual position 50000 ``` But I expected this output instead: ``` Copied 10000, Expected position 10000, actual position 10000 Copied 10000, Expected position 20000, actual position 20000 Copied 10000, Expected position 30000, actual position 30000 Copied 8192, Expected position 38192, actual position 38192 Copied 10000, Expected position 48192, actual position 48192 ``` Notice how, in the real output, when the dot appears after 30000 (suggesting 0 bytes were copied, in fact 8192 bytes appear to have been copied according to the position returned by ftell()) - you can confirm $copied is false by uncommenting the relevant lines. Also note that $streaminput never got to an eof state, and appeared most time to have simply stopped adding to the stream, and I end up killing the php script with ^C ### PHP Version PHP 8.1.2-1ubuntu2.13 (cli) (built: Jun 28 2023 14:01:49) (NTS) ### Operating System Ubuntu 22.04.2 LTS \n \l (running on WSL in Windows 11)