PathMatchSpec Problems

Today I was debugging a problem in my application where a wildcard name failed to match. I traced the problem to significant issues with the implementation of PathMatchSpec() in the Windows API.

In short, do not expect this function to work like the command interpreter Cmd.exe. This function does not handle many boundary conditions, nor does it properly handle empty extensions.

The simplest example is this command, which correctly finds the Windows directory on all versions of Windows and MS-DOS 6.x:

dir c:\windows.*

However, this API call returns false on Vista:

BOOL b = ::PathMatchSpec("C:\\Windows", "C:\\Windows.*");

Other inconsistencies are shown in the table below. The "right" answer to these scenarios is unclear because MS-DOS did not support long filenames or spaces in filenames. Although various versions of Windows are themselves inconsistent, PathMatchSpec() does not agree with any of them. I would argue that the correct behavior is what Windows Vista does.

Command	::PathMatchSpec("C:\\Windows", xxx);	MS-DOS	Win 9x	Win NT
dir c:\windows.*	False	Displays directory name	Displays directory name	Displays directory name
dir c:\windows.	False	Displays directory contents	Displays directory contents	Displays directory contents
dir c:\windows...	False	Displays directory name	Displays directory contents	Fail
dir "c:\windows " (Note the trailing space)	False	n/a	Displays directory contents	Fail
dir "c:\windows ." (Note the trailing space followed by a period.)	False	n/a	Displays directory contents	Fail

And yes, I did actually install MS-DOS to create this chart :-)