public void addExternalEntryPointRef(Address toAddr) throws IllegalArgumentException {
		if (!toAddr.isMemoryAddress()) {
			throw new IllegalArgumentException("Entry point address must be memory address");
		}
		if (!isExternalEntryPoint(toAddr)) {
			try {
				addRef(Address.EXT_FROM_ADDRESS, toAddr, RefType.EXTERNAL_REF, SourceType.DEFAULT,
					CodeUnit.MNEMONIC, false, false, 0);
			}
			catch (IOException e) {
				program.dbError(e);
			}
			externalEntryPointAdded(toAddr);
		}
	}
Create a memory reference to the given address to mark it as
an external entry point.
@param toAddr the address at which to make an external entry point
@throws IllegalArgumentException if a non-memory address is specified
Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/database/references/ReferenceDBManager.java