* shortcut.c: New file. Provides a C interface to reading of

Windows shortcuts to avoid compiler flag `-fvtable-thunks'.
        * shortcut.h: Ditto.
        * Makefile.in: Add shortcut.o to DLL_OFILES.
        * cygerrno.h: Provide a C interface to `geterrno_from_win_error' for
        using in shortcut.c.
        * errno.cc (geterrno_from_win_error): Define as extern "C".
        * path.cc (struct symlink_info): Remove methods `check_shortcut' and
        `check_sysfile'.
        (shortcut_header): Move to shortcut.c.
        (shortcut_initalized): Ditto.
        (create_shortcut_header): Ditto.
        (cmp_shortcut_header): Ditto.
        (symlink_info::check_shortcut): Ditto. Reorganize as a plain C function.
        (symlink_info::check_sysfile): Redefine as a global function using the
        same parameter list as `check_shortcut' for clearness.
        (symlink_info::check): Change parameter list for calls to
        `check_shortcut' and `check_sysfile'.

winsup/cygwin/shortcut.c

@@ -0,0 +1,171 @@
+/* shortcut.c: Read shortcuts. This part of the code must be in C because
+               the C++ interface to COM doesn't work without -fvtable-thunk
+	       which is too dangerous to use.
+
+   Copyright 2001 Red Hat, Inc.
+
+This file is part of Cygwin.
+
+This software is a copyrighted work licensed under the terms of the
+Cygwin license.  Please consult the file "CYGWIN_LICENSE" for
+details. */
+
+#include "winsup.h"
+#include <shlobj.h>
+#include <ctype.h>
+#include <sys/types.h>
+#include <sys/mount.h>
+#include <errno.h>
+#include "cygerrno.h"
+#include "shortcut.h"
+
+/* This is needed to avoid including path.h which is a pure C++ header. */
+#define PATH_SYMLINK MOUNT_SYMLINK
+
+#define debug_printf(x) strcpy (contents, x)
+
+char shortcut_header[SHORTCUT_HDR_SIZE];
+BOOL shortcut_initalized = FALSE;
+
+void
+create_shortcut_header (void)
+{
+  if (!shortcut_initalized)
+    {
+      shortcut_header[0] = 'L';
+      shortcut_header[4] = '\001';
+      shortcut_header[5] = '\024';
+      shortcut_header[6] = '\002';
+      shortcut_header[12] = '\300';
+      shortcut_header[19] = 'F';
+      shortcut_header[20] = '\f';
+      shortcut_header[60] = '\001';
+      shortcut_initalized = TRUE;
+    }
+}
+
+static BOOL
+cmp_shortcut_header (const char *file_header)
+{
+  create_shortcut_header ();
+  return memcmp (shortcut_header, file_header, SHORTCUT_HDR_SIZE);
+}
+
+int
+check_shortcut (const char *path, DWORD fileattr, HANDLE h,
+		char *contents, int *error, unsigned *pflags)
+{
+  HRESULT hres;
+  IShellLink *psl = NULL;
+  IPersistFile *ppf = NULL;
+  WCHAR wc_path[MAX_PATH];
+  char full_path[MAX_PATH];
+  WIN32_FIND_DATA wfd;
+  DWORD len = 0;
+  int res = 0;
+
+  /* Initialize COM library. */
+  CoInitialize (NULL);
+
+  /* Get a pointer to the IShellLink interface. */
+  hres = CoCreateInstance (&CLSID_ShellLink, NULL, CLSCTX_INPROC_SERVER,
+			   &IID_IShellLink, (void **)&psl);
+  if (FAILED (hres))
+    {
+      debug_printf ("CoCreateInstance failed");
+      goto close_it;
+    }
+  /* Get a pointer to the IPersistFile interface. */
+  hres = psl->lpVtbl->QueryInterface (psl, &IID_IPersistFile, (void **)&ppf);
+  if (FAILED (hres))
+    {
+      debug_printf ("QueryInterface failed");
+      goto close_it;
+    }
+  /* Load the shortcut. */
+  MultiByteToWideChar(CP_ACP, 0, path, -1, wc_path, MAX_PATH);
+  hres = ppf->lpVtbl->Load (ppf, wc_path, STGM_READ);
+  if (FAILED (hres))
+    {
+      debug_printf ("Load failed");
+      goto close_it;
+    }
+  /* Try the description (containing a POSIX path) first. */
+  if (fileattr & FILE_ATTRIBUTE_READONLY)
+    {
+      /* An additional check is needed to prove if it's a shortcut
+         really created by Cygwin or U/WIN. */
+      char file_header[SHORTCUT_HDR_SIZE];
+      DWORD got;
+
+      if (! ReadFile (h, file_header, SHORTCUT_HDR_SIZE, &got, 0))
+	{
+	  debug_printf ("ReadFile failed");
+          *error = EIO;
+	  goto close_it_dont_set_error;
+	}
+      if (got == SHORTCUT_HDR_SIZE && !cmp_shortcut_header (file_header))
+        {
+	  hres = psl->lpVtbl->GetDescription (psl, contents, MAX_PATH);
+	  if (FAILED (hres))
+	    {
+	      debug_printf ("GetDescription failed");
+	      goto close_it;
+	    }
+	  len = strlen (contents);
+	}
+    }
+  /* No description or not R/O: Check the "official" path. */
+  if (len == 0)
+    {
+      /* Convert to full path (easy way) */
+      if ((path[0] == '\\' && path[1] == '\\')
+	  || (_toupper (path[0]) >= 'A' && _toupper (path[0]) <= 'Z'
+	      && path[1] == ':'))
+	len = 0;
+      else
+	{
+	  len = GetCurrentDirectory (MAX_PATH, full_path);
+	  if (path[0] == '\\')
+	    len = 2;
+	  else if (full_path[len - 1] != '\\')
+	    strcpy (full_path + len++, "\\");
+	}
+      strcpy (full_path + len, path);
+      /* Set relative path inside of IShellLink interface. */
+      hres = psl->lpVtbl->SetRelativePath (psl, full_path, 0);
+      if (FAILED (hres))
+	{
+	  debug_printf ("SetRelativePath failed");
+	  goto close_it;
+	}
+      /* Get the path to the shortcut target. */
+      hres = psl->lpVtbl->GetPath (psl, contents, MAX_PATH, &wfd, 0);
+      if (FAILED(hres))
+	{
+	  debug_printf ("GetPath failed");
+	  goto close_it;
+	}
+    }
+  /* It's a symlink.  */
+  *pflags = PATH_SYMLINK;
+  res = strlen (contents);
+
+close_it:
+  if (FAILED (hres))
+    *error = geterrno_from_win_error (HRESULT_CODE (hres), EACCES);
+
+close_it_dont_set_error:
+  /* Release the pointer to IPersistFile. */
+  if (ppf)
+    ppf->lpVtbl->Release(ppf);
+  /* Release the pointer to IShellLink. */
+  if (psl)
+    psl->lpVtbl->Release(psl);
+  /* Uninitialize COM library. */
+  CoUninitialize ();
+
+  return res;
+}
+
+