[PATCH v2 0/2] Handle "app execution aliases"

Corinna Vinschen corinna-cygwin@cygwin.com
Tue Mar 23 15:58:53 GMT 2021


On Mar 22 16:51, Johannes Schindelin via Cygwin-patches wrote:
> When installing e.g. Python via the Windows Store, it is common that the
> `python3.exe` entry in the `PATH` is not actually an executable at all,
> but an "app executaion alias" (i.e. a special class of reparse point).
> 
> These filesystem entries are presented as 0-size files, but they are not
> readable, which is why Cygwin has problems to execute them, with the error
> message "Permission denied".
> 
> This issue has been reported a couple of times in the Git for Windows and
> in the MSYS2 project, and even in Cygwin
> (https://cygwin.com/pipermail/cygwin/2020-May/244969.html, the thread
> devolved into a discussion about Thunderbird vs Outlook before long,
> though).
> 
> The second patch fixes that, and for good measure, the first patch teaches
> Cygwin to treat these reparse points as symbolic links.
> 
> Changes since v1:
> 
> - Introduce and use `struct _REPARSE_APPEXECLINK_BUFFER`.
> 
> Johannes Schindelin (2):
>   Treat Windows Store's "app execution aliases" as symbolic links
>   Allow executing Windows Store's "app execution aliases"
> 
>  winsup/cygwin/path.cc  | 40 ++++++++++++++++++++++++++++++++++++++++
>  winsup/cygwin/spawn.cc |  7 +++++++
>  2 files changed, 47 insertions(+)

I decided to apply this now, while we're still discussing the osf handle
problem.

Pushed with two fixes.  I prepended "Cygwin:" to the git log subject and
I patched this compile time problem:

  path.cc: In function ‘int check_reparse_point_target(HANDLE, bool, PREPARSE_DATA_BUFFER, PUNICODE_STRING)’:
  path.cc:2581:25: error: ‘struct _REPARSE_APPEXECLINK_BUFFER’ has no member named ‘Strings’
   2581 |       WCHAR *buf = rpl->Strings;
	|                         ^~~~~~~

I also added this to the release notes.


Thanks,
Corinna


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