For thread-safety reasons, the GNU C Library (2.2+) defines "errno" as a macro that calls a function to get the errno of the current thread. Consequently, the source file "src/runtime/Builtin/cIOExtras.c" needs to include the header file, rather than declaring an extern variable. Diff: ========================================================================== *** cIOExtras.old.c Wed May 23 14:54:58 2001 --- cIOExtras.c Wed May 23 14:26:54 2001 *************** *** 1,10 **** /* basic unsafe utilities, defined in IOExtras */ #include "cinterface.h" #include "mk.h" void performGC () { C_GC(0); } int unsafePtrEq (void* a, void* b) { return (a==b); } /* basic error handling via C's errno */ ! extern int errno; int getErrNo (void) { return errno; } --- 1,11 ---- /* basic unsafe utilities, defined in IOExtras */ #include "cinterface.h" #include "mk.h" + #include "errno.h" void performGC () { C_GC(0); } int unsafePtrEq (void* a, void* b) { return (a==b); } /* basic error handling via C's errno */ ! /*extern int errno;*/ int getErrNo (void) { return errno; }