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Re: [ID 19990914.001] Perl_re_intuit_start() hangs in a loop
authorIlya Zakharevich <ilya@math.berkeley.edu>
Tue, 14 Sep 1999 21:26:15 +0000 (17:26 -0400)
committerGurusamy Sarathy <gsar@cpan.org>
Wed, 15 Sep 1999 01:27:14 +0000 (01:27 +0000)
Message-Id: <199909150126.VAA24720@monk.mps.ohio-state.edu>

p4raw-id: //depot/perl@4158

regexec.c
t/op/pat.t

index 8361145..d55c5be 100644 (file)
--- a/regexec.c
+++ b/regexec.c
@@ -278,7 +278,16 @@ S_cache_re(pTHX_ regexp *prog)
 /* A failure to find a constant substring means that there is no need to make
    an expensive call to REx engine, thus we celebrate a failure.  Similarly,
    finding a substring too deep into the string means that less calls to
-   regtry() should be needed. */
+   regtry() should be needed.
+
+   REx compiler's optimizer found 4 possible hints:
+       a) Anchored substring;
+       b) Fixed substring;
+       c) Whether we are anchored (beginning-of-line or \G);
+       d) First node (of those at offset 0) which may distingush positions;
+   We use 'a', 'b', multiline-part of 'c', and try to find a position in the
+   string which does not contradict any of them.
+ */
 
 char *
 Perl_re_intuit_start(pTHX_ regexp *prog, SV *sv, char *strpos,
@@ -293,6 +302,9 @@ Perl_re_intuit_start(pTHX_ regexp *prog, SV *sv, char *strpos,
     I32 ml_anch;
     char *tmp;
     register char *other_last = Nullch;
+#ifdef DEBUGGING
+    char *i_strpos = strpos;
+#endif
 
     DEBUG_r( if (!PL_colorset) reginitcolors() );
     DEBUG_r(PerlIO_printf(Perl_debug_log,
@@ -420,7 +432,7 @@ Perl_re_intuit_start(pTHX_ regexp *prog, SV *sv, char *strpos,
        goto fail_finish;
 
     /* Finish the diagnostic message */
-    DEBUG_r(PerlIO_printf(Perl_debug_log, "%ld...\n", (long)(s - strpos)) );
+    DEBUG_r(PerlIO_printf(Perl_debug_log, "%ld...\n", (long)(s - i_strpos)) );
 
     /* Got a candidate.  Check MBOL anchoring, and the *other* substr.
        Start with the other substr.
@@ -431,11 +443,13 @@ Perl_re_intuit_start(pTHX_ regexp *prog, SV *sv, char *strpos,
      */
 
     if (prog->float_substr && prog->anchored_substr) {
-       /* Take into account the anchored substring. */
+       /* Take into account the "other" substring. */
        /* XXXX May be hopelessly wrong for UTF... */
        if (!other_last)
            other_last = strpos - 1;
        if (check == prog->float_substr) {
+         do_other_anchored:
+           {
                char *last = s - start_shift, *last1, *last2;
                char *s1 = s;
 
@@ -446,7 +460,7 @@ Perl_re_intuit_start(pTHX_ regexp *prog, SV *sv, char *strpos,
                        || (PL_bostr = strpos, /* Used in regcopmaybe() */
                            (t = reghopmaybe_c(s, -(prog->check_offset_max)))
                            && t > strpos)))
-                   ;
+                   /* EMPTY */;
                else
                    t = strpos;
                t += prog->anchored_offset;
@@ -478,7 +492,7 @@ Perl_re_intuit_start(pTHX_ regexp *prog, SV *sv, char *strpos,
                    }
                    DEBUG_r(PerlIO_printf(Perl_debug_log,
                        ", trying floating at offset %ld...\n",
-                       (long)(s1 + 1 - strpos)));
+                       (long)(s1 + 1 - i_strpos)));
                    PL_regeol = strend;                 /* Used in HOP() */
                    other_last = last1 + prog->anchored_offset;
                    s = HOPc(last, 1);
@@ -486,14 +500,15 @@ Perl_re_intuit_start(pTHX_ regexp *prog, SV *sv, char *strpos,
                }
                else {
                    DEBUG_r(PerlIO_printf(Perl_debug_log, " at offset %ld...\n",
-                         (long)(s - strpos)));
+                         (long)(s - i_strpos)));
                    t = s - prog->anchored_offset;
                    other_last = s - 1;
+                   s = s1;
                    if (t == strpos)
                        goto try_at_start;
-                   s = s1;
                    goto try_at_offset;
                }
+           }
        }
        else {          /* Take into account the floating substring. */
                char *last, *last1;
@@ -529,7 +544,7 @@ Perl_re_intuit_start(pTHX_ regexp *prog, SV *sv, char *strpos,
                    }
                    DEBUG_r(PerlIO_printf(Perl_debug_log,
                        ", trying anchored starting at offset %ld...\n",
-                       (long)(s1 + 1 - strpos)));
+                       (long)(s1 + 1 - i_strpos)));
                    other_last = last;
                    PL_regeol = strend;                 /* Used in HOP() */
                    s = HOPc(t, 1);
@@ -537,11 +552,11 @@ Perl_re_intuit_start(pTHX_ regexp *prog, SV *sv, char *strpos,
                }
                else {
                    DEBUG_r(PerlIO_printf(Perl_debug_log, " at offset %ld...\n",
-                         (long)(s - strpos)));
+                         (long)(s - i_strpos)));
                    other_last = s - 1;
+                   s = s1;
                    if (t == strpos)
                        goto try_at_start;
-                   s = s1;
                    goto try_at_offset;
                }
        }
@@ -559,18 +574,36 @@ Perl_re_intuit_start(pTHX_ regexp *prog, SV *sv, char *strpos,
           cannot start at strpos. */
       try_at_offset:
        if (ml_anch && t[-1] != '\n') {
-         find_anchor:          /* Eventually fbm_*() should handle this */
+           /* Eventually fbm_*() should handle this, but often
+              anchored_offset is not 0, so this check will not be wasted. */
+           /* XXXX In the code below we prefer to look for "^" even in
+              presence of anchored substrings.  And we search even
+              beyond the found float position.  These pessimizations
+              are historical artefacts only.  */
+         find_anchor:
            while (t < strend - prog->minlen) {
                if (*t == '\n') {
                    if (t < s - prog->check_offset_min) {
+                       if (prog->anchored_substr) {
+                           /* We definitely contradict the found anchored
+                              substr.  Due to the above check we do not
+                              contradict "check" substr.
+                              Thus we can arrive here only if check substr
+                              is float.  Redo checking for "other"=="fixed".
+                            */
+                           strpos = t + 1;                         
+                           DEBUG_r(PerlIO_printf(Perl_debug_log, "Found /%s^%s/m at offset %ld, rescanning for anchored from offset %ld...\n",
+                               PL_colors[0],PL_colors[1], (long)(strpos - i_strpos), (long)(strpos - i_strpos + prog->anchored_offset)));
+                           goto do_other_anchored;
+                       }
                        s = t + 1;
                        DEBUG_r(PerlIO_printf(Perl_debug_log, "Found /%s^%s/m at offset %ld...\n",
-                           PL_colors[0],PL_colors[1], (long)(s - strpos)));
+                           PL_colors[0],PL_colors[1], (long)(s - i_strpos)));
                        goto set_useful;
                    }
                    DEBUG_r(PerlIO_printf(Perl_debug_log, "Found /%s^%s/m, restarting at offset %ld...\n",
-                       PL_colors[0],PL_colors[1], (long)(t + 1 - strpos)));
-                   s = t + 1;
+                       PL_colors[0],PL_colors[1], (long)(t + 1 - i_strpos)));
+                   strpos = s = t + 1;
                    goto restart;
                }
                t++;
@@ -596,8 +629,12 @@ Perl_re_intuit_start(pTHX_ regexp *prog, SV *sv, char *strpos,
            t = strpos;
            goto find_anchor;
        }
+       DEBUG_r( if (ml_anch)
+           PerlIO_printf(Perl_debug_log, "Does not contradict /%s^%s/m...\n",
+                       PL_colors[0],PL_colors[1]);
+       );
       success_at_start:
-       if (!(prog->reganch & ROPT_NAUGHTY)
+       if (!(prog->reganch & ROPT_NAUGHTY)     /* XXXX If strpos moved? */
            && --BmUSEFUL(prog->check_substr) < 0
            && prog->check_substr == prog->float_substr) { /* boo */
            /* If flags & SOMETHING - do not do it many times on the same match */
@@ -612,7 +649,7 @@ Perl_re_intuit_start(pTHX_ regexp *prog, SV *sv, char *strpos,
     }
 
     DEBUG_r(PerlIO_printf(Perl_debug_log, "%sGuessed:%s match at offset %ld\n",
-                         PL_colors[4], PL_colors[5], (long)(s - strpos)) );
+                         PL_colors[4], PL_colors[5], (long)(s - i_strpos)) );
     return s;
 
   fail_finish:                         /* Substring not found */
@@ -755,9 +792,12 @@ Perl_regexec_flags(pTHX_ register regexp *prog, char *stringarg, register char *
            end = HOPc(strend, -dontbother) - 1;
            /* for multiline we only have to try after newlines */
            if (prog->check_substr) {
+               if (s == startpos)
+                   goto after_try;
                while (1) {
                    if (regtry(prog, s))
                        goto got_it;
+                 after_try:
                    if (s >= end)
                        goto phooey;
                    s = re_intuit_start(prog, sv, s + 1, strend, flags, NULL);
index 768d1b9..89cc2bb 100755 (executable)
@@ -4,7 +4,7 @@
 # the format supported by op/regexp.t.  If you want to add a test
 # that does fit that format, add it to op/re_tests, not here.
 
-print "1..191\n";
+print "1..192\n";
 
 BEGIN {
     chdir 't' if -d 't';
@@ -882,3 +882,8 @@ print "not " unless $1 eq "{ and }";
 print "ok $test\n";
 $test++;
 
+$_ = "a-a\nxbb";
+pos=1;
+m/^-.*bb/mg and print "not ";
+print "ok $test\n";
+$test++;