Why “The system cannot find the batch label specified” is thrown even if label exists?

Question

While running a batch file in Windows XP I have found randomly occurring error message:

The system cannot find the batch label specified name_of_label

Answer 1

There are multiple possible ways to get the error.

1. Described by VonC - Wrong line endings, LF instead of CR/LF

2. Obscure long lines (if that happens accidential, your code is incredible worse)

3. Direct start another batch after calling a function.
   Sample:

   @echo off
   call :func
   echo back from second
   exit /b
   
   :func
   second.bat
   echo NEVER COME BACK HERE

   This unexpectedly tries to goto to the label :func in second.bat.
   But this can be (mis)-used to directly call labels in another batch file

This is the described behaviour of the answer of Marshal