Partial fix for bug #61 "empty character class [] matches empty string".

Given the following code:
    /*!re2c
        [] {}
    */

    /*!re2c
        [^\x00-\xFF] {}
    */

    /*!re2c
        [\x00-\xFF]\[\x00-\xFF] {}
    */
re2c versions <=0.13.6 and >=0.13.7 behaved differently.
0.13.6 consistently considered that empty range should match empty string.
Since 0.13.7 empty positive range [] and empty difference (e.g. [a-z][a-z])
still match empty string, but empty negative range (e.g. [^\x00-\xFF])
matches nothing (always fails). The faulty commit is
28ee7c95bca46ad3cdb965741c5c29e21c50df14
"Added UTF-8 encoding support and tests for it."

This commit brings back consistent behaviour of 0.13.6: empty range,
however it was constructed, always matches empty string. Whether this
behaviour is sane or not is another question.

diff --git a/re2c/src/ir/regexp/regexp.cc b/re2c/src/ir/regexp/regexp.cc
index 3eade194cc1acaf2735c86dddcfc4a2b7ba9c771..d259531f16e4f830fae77ae744d79461c464cd4a 100644 (file)
--- a/re2c/src/ir/regexp/regexp.cc
+++ b/re2c/src/ir/regexp/regexp.cc
@@ -106,20 +106,6 @@ RegExp * doCat (RegExp * e1, RegExp * e2)
        return new CatOp (e1, e2);
 }
 
-RegExp * mkDiff (RegExp * e1, RegExp * e2)
-{
-       MatchOp * m1 = dynamic_cast<MatchOp *> (e1);
-       MatchOp * m2 = dynamic_cast<MatchOp *> (e2);
-       if (m1 == NULL || m2 == NULL)
-       {
-               return NULL;
-       }
-       Range * r = range_diff (m1->match, m2->match);
-       return r
-               ? (RegExp *) new MatchOp(r)
-               : (RegExp *) new NullOp;
-}
-
 Range * Scanner::getRange(SubStr &s) const
 {
        uint32_t lb = unescape(s), ub;
@@ -223,6 +209,11 @@ Range * Scanner::mkRange(SubStr &s) const
 
 RegExp * Scanner::matchSymbolRange(Range * r) const
 {
+       if (!r)
+       {
+               return new NullOp;
+       }
+
        if (encoding.is(Enc::UTF16))
                return UTF16Range(r);
        else if (encoding.is(Enc::UTF8))
@@ -236,10 +227,11 @@ RegExp * Scanner::ranToRE (SubStr & s) const
        s.len -= 2;
        s.str += 1;
 
-       if (s.len == 0)
-               return new NullOp;
+       Range * r = s.len == 0
+               ? NULL
+               : mkRange(s);
 
-       return matchSymbolRange(mkRange(s));
+       return matchSymbolRange (r);
 }
 
 RegExp * Scanner::invToRE (SubStr & s) const
@@ -256,6 +248,19 @@ RegExp * Scanner::invToRE (SubStr & s) const
        return matchSymbolRange(r);
 }
 
+RegExp * Scanner::mkDiff (RegExp * e1, RegExp * e2) const
+{
+       MatchOp * m1 = dynamic_cast<MatchOp *> (e1);
+       MatchOp * m2 = dynamic_cast<MatchOp *> (e2);
+       if (m1 == NULL || m2 == NULL)
+       {
+               fatal("can only difference char sets");
+       }
+       Range * r = range_diff (m1->match, m2->match);
+
+       return matchSymbolRange (r);
+}
+
 RegExp * Scanner::mkDot() const
 {
        Range * full = encoding.fullRange();

diff --git a/re2c/src/ir/regexp/regexp.h b/re2c/src/ir/regexp/regexp.h
index 758d3b4f2b01ed3c71e5c5990ed4be50fd29a7d7..a5323146a3f02b4a4d78c055ebe666194f8d0142 100644 (file)
--- a/re2c/src/ir/regexp/regexp.h
+++ b/re2c/src/ir/regexp/regexp.h
@@ -69,7 +69,6 @@ public:
 RegExp * doAlt (RegExp * e1, RegExp * e2);
 RegExp * mkAlt (RegExp * e1, RegExp * e2);
 RegExp * doCat (RegExp * e1, RegExp * e2);
-RegExp * mkDiff (RegExp * e1, RegExp * e2);
 
 } // end namespace re2c
 

diff --git a/re2c/src/parse/parser.ypp b/re2c/src/parse/parser.ypp
index 114ad9402e692e5364c1395e4ac1effe7e8f78bd..14c3f941dc900cf771de78e8ca089dae65828347 100644 (file)
--- a/re2c/src/parse/parser.ypp
+++ b/re2c/src/parse/parser.ypp
@@ -404,11 +404,7 @@ diff:
                }
        |       diff '\\' term
                {
-                       $$ = mkDiff($1, $3);
-                       if(!$$)
-                       {
-                               in->fatal("can only difference char sets");
-                       }
+                       $$ = in->mkDiff($1, $3);
                }
 ;
 

diff --git a/re2c/src/parse/scanner.h b/re2c/src/parse/scanner.h
index 51236b5a112d8176527a2f7da9dbafc268770f55..21e98e9143c891f3918ccdb4d7da183ccd02b4e4 100644 (file)
--- a/re2c/src/parse/scanner.h
+++ b/re2c/src/parse/scanner.h
@@ -93,6 +93,7 @@ public:
        RegExp * strToCaseInsensitiveRE (SubStr & s) const;
        RegExp * ranToRE (SubStr & s) const;
        RegExp * invToRE (SubStr & s) const;
+       RegExp * mkDiff (RegExp * e1, RegExp * e2) const;
        RegExp * mkDot () const;
        RegExp * mkDefault () const;
 

diff --git a/re2c/test/bug61.i.c b/re2c/test/bug61.i.c
new file mode 100644 (file)
index 0000000..453370d
--- /dev/null
+++ b/re2c/test/bug61.i.c
@@ -0,0 +1,21 @@
+/* Generated by re2c */
+
+{
+       YYCTYPE yych;
+       {}
+}
+
+
+
+{
+       YYCTYPE yych;
+       {}
+}
+
+
+
+{
+       YYCTYPE yych;
+       {}
+}
+

diff --git a/re2c/test/bug61.i.re b/re2c/test/bug61.i.re
new file mode 100644 (file)
index 0000000..4937d7d
--- /dev/null
+++ b/re2c/test/bug61.i.re
@@ -0,0 +1,11 @@
+/*!re2c
+    [] {}
+*/
+
+/*!re2c
+    [^\x00-\xFF] {}
+*/
+
+/*!re2c
+    [\x00-\xFF]\[\x00-\xFF] {}
+*/

diff --git a/re2c/test/bug61a.i.c b/re2c/test/bug61a.i.c
new file mode 100644 (file)
index 0000000..39becbe
--- /dev/null
+++ b/re2c/test/bug61a.i.c
@@ -0,0 +1 @@
+re2c: error: line 14, column 31: can only difference char sets

diff --git a/re2c/test/bug61a.i.re b/re2c/test/bug61a.i.re
new file mode 100644 (file)
index 0000000..0e00561
--- /dev/null
+++ b/re2c/test/bug61a.i.re
@@ -0,0 +1,15 @@
+/*!re2c
+    [] {}
+*/
+
+/*!re2c
+    [^\x00-\xFF] {}
+*/
+
+/*!re2c
+    [\x00-\xFF]\[\x00-\xFF] {}
+*/
+
+/*!re2c
+    [^\x00-\xFF]\[^\x00-\xFF] {}
+*/