You must upgrade your ACS compiler to use ACSUtils because the official ACC 1.55 release can't compile files with more than 256 functions.

Upgrade to one of the following compilers:

• ACC 1.56 Beta: DOWNLOAD. This archive also includes the latest Zandronum zcommon from https://github.com/Korshun/zcommon.
• BCC
• GDCC

1. Download the latest release.
2. Add acsutils.acs to your project.
3. Include acsutils.acs after zcommon.acs:

#include "zcommon.acs"
#include "acsutils.acs"

If your project has functions (or variables, if you are using ACC) with the same names as ACSUtils functions, it won't compile. Rename the functions in your project to fix it. ACSUtils functions are named to avoid some of the most annoying conflicts, but it still needs several renames in some big projects.

1. Copy decorate/changeflag.txt to your decorate and #include it to make ChangeFlag and ChangeActorFlag work.
2. Copy cvarinfo.acsutils to your project root to allow the server to hide ACSUtils errors using the acsutils_noerrors cvar (it will automatically load and not conflict with your mod's CVARINFO because ZDoom ignores the extension).

If you are using BCC, try BCSUtils – a BCC-enhanced version of ACSUtils with the same functions!