Hi all, The attached e-mail seems to be about a problem using a library compiled with an unregisterised ghc with a registerised ghc. The linking step is giving many "undefined reference to `stg_ap_p_ret'"s (with various numbers of 'p's) as well as a few to `GHCziIOBase_zdWIO_entry', and possible others I didn't spot, while compiling haskelldb with a registerised ghc 6.4.1, where haskelldb depends on hsql, which was compiled with an unregisterised ghc 6.4.1. Is this expected behaviour? i.e. should I just make sure I don't change which arches are registerised within a GHC version? If so, would a library compiled with a registerised ghc being used by an unregisterised ghc also cause problems? Or have I got the problem completely wrong? Based on a quick look at the GHC source, the missing symbols seem to be due to this, in ghc/rts/Linker.c : #ifdef TABLES_NEXT_TO_CODE #define RTS_RET_SYMBOLS /* nothing */ #else #define RTS_RET_SYMBOLS \ [...] SymX(stg_ap_p_ret) \ [...] #endif being toggled due to this, in ghc/includes/RtsConfig.h : #if !defined(USE_MINIINTERPRETER) && !defined(ia64_HOST_ARCH) && !defined (powerpc64_HOST_ARCH) #define TABLES_NEXT_TO_CODE #endif in turn due to this, in ghc/includes/Makefile : ifeq "$(GhcUnregisterised)" "YES" SRC_CC_OPTS += -DNO_REGS -DUSE_MINIINTERPRETER endif Thanks Ian