add -DPERL_Y2KWARN build option that will generate additional

warnings on "19$yy" etc (reworked a patch suggested by
Ulrich Pfeifer <upf@de.uu.net>)

p4raw-id: //depot/perl@4132

1 files changed, 13 insertions, 0 deletions

diff --git a/sv.c b/sv.c
index acded3146d..b21c9edf43 100644
--- a/sv.c
+++ b/sv.c
@@ -5037,6 +5037,19 @@ Perl_sv_vcatpvfn(pTHX_ SV *sv, const char *pat, STRLEN patlen, va_list *args, SV
 		    *--eptr = '0';
 		break;
 	    default:		/* it had better be ten or less */
+#if defined(PERL_Y2KWARN)
+		if (ckWARN(WARN_MISC)) {
+		    STRLEN n;
+		    char *s = SvPV(sv,n);
+		    if (n >= 2 && s[n-2] == '1' && s[n-1] == '9'
+			&& (n == 2 || !isDIGIT(s[n-3])))
+		    {
+			Perl_warner(aTHX_ WARN_MISC,
+				    "Possible Y2K bug: %%%c %s",
+				    c, "format string following '19'");
+		    }
+		}
+#endif
 		do {
 		    dig = uv % base;
 		    *--eptr = '0' + dig;