win32: more problems with stream i/o and MSVCRT

These commands:

   cut --wrong-opt 2>&1
   echo $(cut --wrong-opt 2>&1)

resulted in different output.  In the first case the message about
the invalid option appeared before the usage message; in the second
after.

The command

   uname --wrong-opt 1>&- 2>&-

displayed the error message even though both output streams were
closed.

These issues appear to be related to those previously fixed by
commits 4be93f32f and f192e6539:

- They involve the interaction between shell redirection and stream
  input/output.

- UCRT builds aren't affected.

Apply two workarounds:

- When the file descriptor associated with stderr is redirected
  remind stderr it should be unbuffered.  (32- and 64-bit MSVCRT)

- When the file descriptor associated with any of the standard i/o
  streams is to be closed do it by closing the stream instead.
  (32-bit MSVCRT)

Adds 48-176 bytes.

(GitHub commit #472)

1 files changed, 16 insertions, 0 deletions

diff --git a/shell/ash.c b/shell/ash.c
index fd2a66270..a5b7dbc74 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -6542,6 +6542,12 @@ save_fd_on_redirect(int fd, int avoid_fd, struct redirtab *sq)
         if (fd == preverrout_fd)
                 preverrout_fd = new_fd;
 
+#if ENABLE_PLATFORM_MINGW32 && !defined(_UCRT)
+        // Workaround for problems with stderr in MSVCRT
+        if (fd == fileno(stderr))
+                setvbuf(stderr, NULL, _IONBF, 0);
+#endif
+
         return 0; /* "we did not close fd" */
 }
 
@@ -6629,6 +6635,16 @@ redirect(union node *redir, int flags)
                         if (!closed) {
                                 /* ^^^ optimization: saving may already
                                  * have closed it. If not... */
+#if ENABLE_PLATFORM_MINGW32 && !defined(_UCRT) && !defined(_WIN64)
+                                // Workaround for problems with streams in 32-bit MSVCRT
+                                if (fd == fileno(stdin))
+                                        fclose(stdin);
+                                else if (fd == fileno(stdout))
+                                        fclose(stdout);
+                                else if (fd == fileno(stderr))
+                                        fclose(stderr);
+                                else
+#endif
                                 close(fd);
                         }
                 } else {