Windows: fix termination of process output redirection (#29923)

The parent thread in the process stdout redirection logic on Windows
was closing a file that was being read in child thread, which lead to
error-based termination of the reader thread. This updates the
interaction to avoid the error.

1 files changed, 16 insertions, 16 deletions

diff --git a/lib/spack/llnl/util/tty/log.py b/lib/spack/llnl/util/tty/log.py
index 544a9a6c48..51b9caa332 100644
--- a/lib/spack/llnl/util/tty/log.py
+++ b/lib/spack/llnl/util/tty/log.py
@@ -809,19 +809,23 @@ class winlog(object):
             def background_reader(reader, echo_writer, _kill):
                 # for each line printed to logfile, read it
                 # if echo: write line to user
-                while True:
-                    is_killed = _kill.wait(.1)
-                    self.stderr.flush()
-                    self.stdout.flush()
-                    line = reader.readline()
-                    while line:
-                        if self.echo:
-                            self.echo_writer.write('{0}'.format(line.decode()))
-                            self.echo_writer.flush()
+                try:
+                    while True:
+                        is_killed = _kill.wait(.1)
+                        # Flush buffered build output to file
+                        # stdout/err fds refer to log file
+                        self.stderr.flush()
+                        self.stdout.flush()
+
                         line = reader.readline()
+                        if self.echo and line:
+                            echo_writer.write('{0}'.format(line.decode()))
+                            echo_writer.flush()
 
-                    if is_killed:
-                        break
+                        if is_killed:
+                            break
+                finally:
+                    reader.close()
 
             self._active = True
             with replace_environment(self.env):
@@ -837,7 +841,6 @@ class winlog(object):
             self._ioflag = False
         else:
             self.writer.close()
-            self.reader.close()
             self.echo_writer.flush()
             self.stdout.flush()
             self.stderr.flush()
@@ -853,10 +856,7 @@ class winlog(object):
         if not self._active:
             raise RuntimeError(
                 "Can't call force_echo() outside log_output region!")
-        try:
-            yield self
-        finally:
-            pass
+        yield
 
 
 def _writer_daemon(stdin_multiprocess_fd, read_multiprocess_fd, write_fd, echo,