I had mistakenly added a source file that had the same function name as a file already in the project. In this case it was a timer handler (callback) function. Functions with scope limited to a single source file should always be preceeded with the static keyword. But in the case thats missing (my mistake) and more than one function with same name, from the eclipse console:
… Link step in progress …
… Link my_project_256KB.bin …
c:\OpenAT\IDE\MINGW\126.96.36.199\bin\make.exe: *** [make_single_bin] Error 1
Had to #if 0 functions one-by-one to find the offending.
So, somewhere is missing the linker error message that warns of duplicately defined function.
(Using SDK 4.22a)