Error -2147221480 Illegal Parameter Name When Compiling DLL in LabVIEW

Updated Nov 20, 2023

Reported In


  • LabVIEW

Operating System

  • Windows

Programming Language

  • C

Issue Details

My VI runs as expected, but when I try to build to a DLL, I am getting multiple C syntax error messages like the following:

An error occurred compiling the DLL because a function or parameter name is illegal. Please verify that the function and/or parameter names are legal C identifiers and do not conflict with LabVIEW headers.
Additional Information: SharedLib.c - 9 errors



In most of the cases, this error is related to a conflict with the name of the variables or the components inside the VI with the 'C' programming language.
In order to solve this issue:
  • Please verify that you are not passing string data with the incorrect method. (See Create LabVIEW DLL to Pass Strings )
  • Review the syntax error that the error message is stating and verify if in some of your VIs there is a component called that way, if so, please re-name all the components and try building your DLL again.
  • Go to DLL >> Properties >> Advanced and deselect the "Include a type library for TestStand or Call Library Nodes" checkbox.
DLL properties.png