testsuite: Pipe stdin directly to process

Previously the driver would read the stdin content from the source file
and then write it to the subprocess' stdin. We now simply open the stdin
file and provide that handle to the subprocess as its stdin

Test Plan: Validate

Reviewers: austin

Subscribers: rwbarton, thomie, goldfire

Differential Revision: https://phabricator.haskell.org/D3735

1 files changed, 5 insertions, 11 deletions

diff --git a/testsuite/driver/testlib.py b/testsuite/driver/testlib.py
index 42122145f5..26e3d17679 100644
--- a/testsuite/driver/testlib.py
+++ b/testsuite/driver/testlib.py
@@ -1792,15 +1792,7 @@ def runCmd(cmd, stdin=None, stdout=None, stderr=None, timeout_multiplier=1.0, pr
     # declare the buffers to a default
     stdin_buffer  = None
 
-    # ***** IMPORTANT *****
-    # We have to treat input and output as
-    # just binary data here. Don't try to decode
-    # it to a string, since we have tests that actually
-    # feed malformed utf-8 to see how GHC handles it.
-    if stdin:
-        with io.open(stdin, 'rb') as f:
-            stdin_buffer = f.read()
-
+    stdin_file = io.open(stdin, 'rb') if stdin else None
     stdout_buffer = b''
     stderr_buffer = b''
 
@@ -1815,12 +1807,14 @@ def runCmd(cmd, stdin=None, stdout=None, stderr=None, timeout_multiplier=1.0, pr
         # to invoke the Bourne shell
 
         r = subprocess.Popen([timeout_prog, timeout, cmd],
-                             stdin=subprocess.PIPE,
+                             stdin=stdin_file,
                              stdout=subprocess.PIPE,
                              stderr=hStdErr)
 
-        stdout_buffer, stderr_buffer = r.communicate(stdin_buffer)
+        stdout_buffer, stderr_buffer = r.communicate()
     finally:
+        if stdin_file:
+            stdin_file.close()
         if config.verbose >= 1 and print_output >= 1:
             if stdout_buffer:
                 sys.stdout.buffer.write(stdout_buffer)