From: Hugo van der Sanden <hv@crypt.org>
Date: Sun, 14 Apr 2002 16:09:30 +0000 (+0100)
Subject: Re: [ID 20020412.005] Dancing ??s
X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=commitdiff_plain;h=d65afb4bb3ed16e1305854aa6e047d2d9d4bb0dd;p=p5sagit%2Fp5-mst-13.2.git

Re: [ID 20020412.005] Dancing ??s
Message-Id: <200204141509.g3EF9UQ18111@crypt.compulink.co.uk>

p4raw-id: //depot/perl@15936
---

diff --git a/pod/perlop.pod b/pod/perlop.pod
index e842317..6785d24 100644
--- a/pod/perlop.pod
+++ b/pod/perlop.pod
@@ -841,7 +841,11 @@ that you won't change the variables in the pattern.  If you change them,
 Perl won't even notice.  See also L<"qr/STRING/imosx">.
 
 If the PATTERN evaluates to the empty string, the last
-I<successfully> matched regular expression is used instead.
+I<successfully> matched regular expression is used instead. In this
+case, only the C<g> and C<c> flags on the empty pattern is honoured -
+the other flags are taken from the original pattern. If no match has
+previously succeeded, this will (silently) act instead as a genuine
+empty pattern (which will always match).
 
 If the C</g> option is not used, C<m//> in list context returns a
 list consisting of the subexpressions matched by the parentheses in the
diff --git a/pp_hot.c b/pp_hot.c
index ec18858..3ff6dc6 100644
--- a/pp_hot.c
+++ b/pp_hot.c
@@ -1184,6 +1184,7 @@ PP(pp_match)
 {
     dSP; dTARG;
     register PMOP *pm = cPMOP;
+    PMOP *dynpm = pm;
     register char *t;
     register char *s;
     char *strend;
@@ -1217,6 +1218,7 @@ PP(pp_match)
 
     PL_reg_match_utf8 = DO_UTF8(TARG);
 
+    /* PMdf_USED is set after a ?? matches once */
     if (pm->op_pmdynflags & PMdf_USED) {
       failure:
 	if (gimme == G_ARRAY)
@@ -1224,17 +1226,19 @@ PP(pp_match)
 	RETPUSHNO;
     }
 
+    /* empty pattern special-cased to use last successful pattern if possible */
     if (!rx->prelen && PL_curpm) {
 	pm = PL_curpm;
 	rx = PM_GETRE(pm);
     }
+
     if (rx->minlen > len)
-      goto failure;
+	goto failure;
 
     truebase = t = s;
 
     /* XXXX What part of this is needed with true \G-support? */
-    if ((global = pm->op_pmflags & PMf_GLOBAL)) {
+    if ((global = dynpm->op_pmflags & PMf_GLOBAL)) {
 	rx->startp[0] = -1;
 	if (SvTYPE(TARG) >= SVt_PVMG && SvMAGIC(TARG)) {
 	    MAGIC* mg = mg_find(TARG, PERL_MAGIC_regex_global);
@@ -1287,8 +1291,8 @@ play_it_again:
     if (CALLREGEXEC(aTHX_ rx, s, strend, truebase, minmatch, TARG, NULL, r_flags))
     {
 	PL_curpm = pm;
-	if (pm->op_pmflags & PMf_ONCE)
-	    pm->op_pmdynflags |= PMdf_USED;
+	if (dynpm->op_pmflags & PMf_ONCE)
+	    dynpm->op_pmdynflags |= PMdf_USED;
 	goto gotcha;
     }
     else
@@ -1325,7 +1329,7 @@ play_it_again:
 	    }
 	}
 	if (global) {
-	    if (pm->op_pmflags & PMf_CONTINUE) {
+	    if (dynpm->op_pmflags & PMf_CONTINUE) {
 		MAGIC* mg = 0;
 		if (SvTYPE(TARG) >= SVt_PVMG && SvMAGIC(TARG))
 		    mg = mg_find(TARG, PERL_MAGIC_regex_global);
@@ -1378,8 +1382,8 @@ yup:					/* Confirmed by INTUIT */
 	RX_MATCH_TAINTED_on(rx);
     TAINT_IF(RX_MATCH_TAINTED(rx));
     PL_curpm = pm;
-    if (pm->op_pmflags & PMf_ONCE)
-	pm->op_pmdynflags |= PMdf_USED;
+    if (dynpm->op_pmflags & PMf_ONCE)
+	dynpm->op_pmdynflags |= PMdf_USED;
     if (RX_MATCH_COPIED(rx))
 	Safefree(rx->subbeg);
     RX_MATCH_COPIED_off(rx);
@@ -1416,7 +1420,7 @@ yup:					/* Confirmed by INTUIT */
 
 nope:
 ret_no:
-    if (global && !(pm->op_pmflags & PMf_CONTINUE)) {
+    if (global && !(dynpm->op_pmflags & PMf_CONTINUE)) {
 	if (SvTYPE(TARG) >= SVt_PVMG && SvMAGIC(TARG)) {
 	    MAGIC* mg = mg_find(TARG, PERL_MAGIC_regex_global);
 	    if (mg)
diff --git a/t/op/pat.t b/t/op/pat.t
index 2ae16c1..853c59c 100755
--- a/t/op/pat.t
+++ b/t/op/pat.t
@@ -6,7 +6,7 @@
 
 $| = 1;
 
-print "1..897\n";
+print "1..900\n";
 
 BEGIN {
     chdir 't' if -d 't';
@@ -2798,3 +2798,28 @@ print "# some Unicode properties\n";
     print eval { "a" =~ /\p{qrst} / } ? "not ok $test\n" : "ok $test\n";
     $test++;
 }
+
+{
+    # [ID 20020412.005] wrong pmop flags checked when empty pattern
+    # requires reuse of last successful pattern
+    my $test = 898;
+    $test =~ /\d/;
+    for (0 .. 1) {
+	my $match = ?? + 0;
+	if ($match != $_) {
+	    print "ok $test\n";
+	} else {
+	    printf "not ok %s\t# 'match once' %s on %s iteration\n", $test,
+		    $match ? 'succeeded' : 'failed', $_ ? 'second' : 'first';
+	}
+	++$test;
+    }
+    $test =~ /(\d)/;
+    my $result = join '', $test =~ //g;
+    if ($result eq $test) {
+	print "ok $test\n";
+    } else {
+	printf "not ok %s\t# expected '%s', got '%s'\n", $test, $test, $result;
+    }
+    ++$test;
+}