gh-82500: Fix asyncio sendfile overflow on 32bit (#107056)

Lib/asyncio/unix_events.py

@@ -394,6 +394,9 @@ class _UnixSelectorEventLoop(selector_events.BaseSelectorEventLoop):
                 fut.set_result(total_sent)
                 return
 
+        # On 32-bit architectures truncate to 1GiB to avoid OverflowError
+        blocksize = min(blocksize, sys.maxsize//2 + 1)
+
         try:
             sent = os.sendfile(fd, fileno, offset, blocksize)
         except (BlockingIOError, InterruptedError):

Misc/NEWS.d/next/Library/2023-07-22-16-44-58.gh-issue-82500.cQYoPj.rst

@@ -0,0 +1 @@
+Fix overflow on 32-bit systems with :mod:`asyncio` :func:`os.sendfile` implemention.