perlio.c cleanup - in particular avoid accidental PerlIO_flush(NULL)

if PerlIONext is NULL.

p4raw-id: //depot/perlio@13975

1 files changed, 1 insertions, 0 deletions

diff --git a/perliol.h b/perliol.h
index 487a7ff164..331cb9514c 100644
--- a/perliol.h
+++ b/perliol.h
@@ -90,6 +90,7 @@ struct _PerlIO {
 #define PerlIOBase(f)      (*(f))
 #define PerlIOSelf(f,type) ((type *)PerlIOBase(f))
 #define PerlIONext(f)      (&(PerlIOBase(f)->next))
+#define PerlIOValid(f)     ((f) && *(f))
 
 /*--------------------------------------------------------------------------------------*/
 /* Data exports - EXT rather than extern is needed for Cygwin */