Return values from wix custom-action dll

I have a .dll I'm using inside a wix-built .msi that is currently returning Windows error codes upon failure. This page seems to imply that I can only use the values listed with dll executables.

The calls are failing (returning non-zero values), but no error message is given to the user. Do I need to modify my 开发者_运维问答.dll to use the "accepted" return values for this to happen?

Yes. See http://msdn.microsoft.com/en-us/library/aa368072%28v=vs.85%29.aspx.