Cygwin: path: Implement path_conv::is_app_execution_alias()

An app execution alias cannot be opened for read (CreateFile() with
GENERIC_READ fails with ERROR_CANT_ACCESS_FILE) because it does not
resolve the reparse point for app execution alias. Therefore, we need
to know if the path is an app execution alias when opening it.

This patch adds new api path_conv::is_app_execution_alias() for
that purpose.

Reviewed-by:
Signed-off-by: Takashi Yano <[email protected]>
Signed-off-by: Johannes Schindelin <[email protected]>

Author: tyan0

winsup/cygwin/local_includes/path.h

@@ -79,6 +79,7 @@ enum path_types
   PATH_SOCKET		= _BIT ( 5),	/* AF_UNIX socket file */
   PATH_RESOLVE_PROCFD	= _BIT ( 6),	/* fd symlink via /proc */
   PATH_REP_NOAPI	= _BIT ( 7),	/* rep. point unknown to WinAPI */
+  PATH_APPEXECLINK	= _BIT ( 8),	/* rep. point app execution alias */
   PATH_DONT_USE		= _BIT (31)	/* conversion to signed happens. */
 };
 
@@ -214,6 +215,10 @@ class path_conv
   {
     return (path_flags & (PATH_REP | PATH_REP_NOAPI)) == PATH_REP;
   }
+  int is_app_execution_alias () const
+  {
+    return path_flags & PATH_APPEXECLINK;
+  }
 
   int isfifo () const {return dev.is_device (FH_FIFO);}
   int iscygdrive () const {return dev.is_device (FH_CYGDRIVE);}

winsup/cygwin/path.cc

@@ -2661,7 +2661,7 @@ check_reparse_point_target (HANDLE h, bool remote, PREPARSE_DATA_BUFFER rp,
 	  if (i == 2 && n > 0 && n < size)
 	    {
 	      RtlInitCountedUnicodeString (psymbuf, buf, n * sizeof (WCHAR));
-	      return PATH_SYMLINK | PATH_REP;
+	      return PATH_SYMLINK | PATH_REP | PATH_APPEXECLINK;
 	    }
 	  if (i == 2)
 	    break;