platform_utils_win32: remove an unnecessary workaround

The comment in _create_symlink is incorrect. The return value of
CreateSymbolicLink is as documented, it was just declared with
the wrong return type. The actual return type is BOOLEAN, not BOOL.

Fixing this allows us to simplify the code a bit.

Change-Id: I4d2190a50d45ba41dd9814bf7079a5784fc0a366

platform_utils_win32.py

@@ -17,7 +17,7 @@ import errno
 
 from ctypes import WinDLL, get_last_error, FormatError, WinError, addressof
 from ctypes import c_buffer
-from ctypes.wintypes import BOOL, LPCWSTR, DWORD, HANDLE, POINTER, c_ubyte
+from ctypes.wintypes import BOOL, BOOLEAN, LPCWSTR, DWORD, HANDLE, POINTER, c_ubyte
 from ctypes.wintypes import WCHAR, USHORT, LPVOID, Structure, Union, ULONG
 from ctypes.wintypes import byref
 
@@ -33,7 +33,7 @@ ERROR_PRIVILEGE_NOT_HELD = 1314
 
 # Win32 API entry points
 CreateSymbolicLinkW = kernel32.CreateSymbolicLinkW
-CreateSymbolicLinkW.restype = BOOL
+CreateSymbolicLinkW.restype = BOOLEAN
 CreateSymbolicLinkW.argtypes = (LPCWSTR,  # lpSymlinkFileName In
                                 LPCWSTR,  # lpTargetFileName In
                                 DWORD)    # dwFlags In
@@ -145,19 +145,12 @@ def create_dirsymlink(source, link_name):
 
 
 def _create_symlink(source, link_name, dwFlags):
-  # Note: Win32 documentation for CreateSymbolicLink is incorrect.
-  # On success, the function returns "1".
-  # On error, the function returns some random value (e.g. 1280).
-  # The best bet seems to use "GetLastError" and check for error/success.
-  CreateSymbolicLinkW(link_name, source, dwFlags | SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE)
-  code = get_last_error()
-  if code != ERROR_SUCCESS:
+  if not CreateSymbolicLinkW(link_name, source, dwFlags | SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE):
     # See https://github.com/golang/go/pull/24307/files#diff-b87bc12e4da2497308f9ef746086e4f0
     # "the unprivileged create flag is unsupported below Windows 10 (1703, v10.0.14972).
     # retry without it."
-    CreateSymbolicLinkW(link_name, source, dwFlags)
-    code = get_last_error()
-    if code != ERROR_SUCCESS:
+    if not CreateSymbolicLinkW(link_name, source, dwFlags):
+      code = get_last_error()
       error_desc = FormatError(code).strip()
       if code == ERROR_PRIVILEGE_NOT_HELD:
         raise OSError(errno.EPERM, error_desc, link_name)