gpython: Support unbuffered mode option -u

gpython/__init__.py

@@ -41,7 +41,7 @@ $GPYTHON_RUNTIME=threads.
 from __future__ import print_function, absolute_import
 
 
-_pyopt = "c:Eim:OvVW:X:"
+_pyopt = "c:Eim:OuvVW:X:"
 _pyopt_long = ('version',)
 
 # pymain mimics `python ...`
@@ -117,6 +117,7 @@ def pymain(argv, init=None):
                 '-O',   # optimize
                 '-v',   # trace import statements
                 '-X',   # set implementation-specific option
+                '-u',   # unbuffered mode
             ):
 
             # but keep `-X gpython.*` in user part of argv in case of reexec

gpython/gpython_test.py

@@ -245,6 +245,45 @@ def test_pymain():
         _,
     )
 
+    # Check -u behaviours
+    if PY2:
+        cmd = ['python2']
+        code = (
+            'import time; '
+            'print(time.time()); '
+            'time.sleep(2); '
+            'print(time.time())'
+        )
+        cmd.extend(['-c', code])
+
+        unbuffer_cmd = cmd[:]
+        unbuffer_cmd.insert(1, '-u')
+    
+        p = subprocess.Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
+        _ = p.stdout.readline().strip()
+        t0 = time.time()
+        _ = p.stdout.readline().strip()
+        t1 = time.time()
+        delay_buffer = t1 - t0
+    
+        u_p = subprocess.Popen(unbuffer_cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
+        _ = u_p.stdout.readline().strip()
+        t3 = time.time()
+        _ = u_p.stdout.readline().strip()
+        t4 = time.time()
+        delay_unbuffer = t1 - t0
+    
+        p.wait()
+        u_p.wait()
+        # Only under unbuffered mode, we can sense the time.sleep(2)
+        # so compare the time difference between unbuffered and buffered
+        assert delay_unbuffer > delay_buffer
+    else:
+        _ = pyout(['-u', '-c', 'import sys; print(sys.stdout.buffer)'], cwd=testdata)
+        assert _ == b"<_io.FileIO name='<stdout>' mode='wb' closefd=False>\n"
+        _ = pyout(['-c', 'import sys; print(sys.stdout.buffer)'], cwd=testdata)
+        assert _ == b"<_io.BufferedWriter name='<stdout>'>\n"
+
 
 def test_pymain_print_function_future():
     if PY2: