Unportable compiler issues: The ICONV_ZERO_MB_STATE_T macro in iconv/lib/local.h seems to be GCC specific. There is also an unusual implementation in libc/iconv/lib/ucsconv.c to reset a mbstate_t data structure.
Created attachment 4452 [details] Patch for ICONV_ZERO_MB_STATE_T macro Here is a suggestion of a more general solution
As mentioned in your other bug, newlib maintainers don't use bugzilla for bugs/patching. It's all done on the mailing list. Please submit your issues and patches directly to the mailing list. It would also help to mention what compiler you are using for future reference.