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

Tue Oct 9 16:52:00 GMT 2018

On 10/9/18 11:21 AM, Dan Kegel wrote:
> 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;

suffices is a completely different word; did you mean suffixes?
> + if ((opt & (O_WRONLY|O_BINARY)) == (O_WRONLY|O_BINARY))

O_WRONLY need not be a bitmask; it's better to use O_ACCMODE for the 
bitmask, as in
 opt & (O_ACCMODE|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)))

So, with mistakes corrected, your hack is that cygwin doing auto-suffix 
probing should be suppressed in the case of opening a file O_WRONLY? Why 
does O_BINARY have to fit in the equation?
> __leave; /* errno already set */
> if ((flags & O_NOFOLLOW) && fh->issymlink ())
> {
>> Feel free to throw rotten fruit :-)
>
-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
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