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 (file)
--- 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 (file)
--- 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 (executable)
--- 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;
+}