Hello,
without any deeper knowledge of your project, it looks like you use some symbols in the .c file, which are not defined in linker file. At first, could you please check, if there was defined some symbols in linker files in CW2.1?
If yes, you must define these symbols in CW11.0 too.
By the way, what library you use? EWL or Newlib?
Could you please eventually share at least some part of project, which shows this error and which should work after this error will be resolved?
Regards,
Martin