Fun with cp -R error when both foo and foo.exe exist

[Dan Kegel]

On Tue, Oct 9, 2018 at 5:03 AM Eric Blake <eblake@redhat.com> wrote:
> whether someone patches the cygwin dll or cp, it seems like some rather
> hairy code for what is normally a rare corner case, so it probably won't
> happen unless someone actually contributes a patch.

Right.  Here's a completely untested guess patch:

--- a/winsup/cygwin/syscalls.cc
+++ b/winsup/cygwin/syscalls.cc
@@ -1363,7 +1363,15 @@ open (const char *unix_path, int flags, ...)
          opt |= PC_CTTY;
        }

-      if (!(fh = build_fh_name (unix_path, opt, stat_suffixes)))
+      suffix_info *suffices = stat_suffixes;
+      if ((opt & (O_WRONLY|O_BINARY)) == (O_WRONLY|O_BINARY))
+        {
+         /* Hack so 'cp foo bar' doesn't abort with
+             'cp: cannot create regular file bar: File exists'
+            if bar.exe already exists  */
+       suffices = NULL;
+       }
+      if (!(fh = build_fh_name (unix_path, opt, suffices)))
        __leave;                /* errno already set */
       if ((flags & O_NOFOLLOW) && fh->issymlink ())
        {

Feel free to throw rotten fruit :-)

- Dan

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