This is the mail archive of the libstdc++@gcc.gnu.org mailing list for the libstdc++ project.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

Re: [libstdc++/71500] make back reference work with icase


On 04/09/17 03:31 -0700, Tim Shen via libstdc++ wrote:
This fixes the follow-up comments in 71500.

Back-reference matching is different from other matching, as the
content the back-reference refers to is at "run-time", aka during
regex_match(), not regex() compilation.

For compilation we do have an abstraction layer to catch all
comparison customizations, namely _M_translator in regex_compiler.h.
Until this patch, we don't have an abstraction for "run-time"
matching. I believe that back-reference is the only place that needs
run-time matching, so I just build a _Backref_matcher in
regex_executot.tcc.

Tested on x86_64-linux-gnu.

Thanks!

--
Regards,
Tim Shen

commit a97b7fecd319e031ffc489a956b8cf3dc63eeb26
Author: Tim Shen <timshen@google.com>
Date:   Mon Sep 4 03:19:35 2017 -0700

           PR libstdc++/71500
           * include/bits/regex_executor.tcc: Support icase in
           regex_tratis<...> for back reference matches.
           * testsuite/28_regex/regression.cc: Test case.

diff --git a/libstdc++-v3/include/bits/regex_executor.tcc b/libstdc++-v3/include/bits/regex_executor.tcc
index 226e05856e1..f6149fecf9d 100644
--- a/libstdc++-v3/include/bits/regex_executor.tcc
+++ b/libstdc++-v3/include/bits/regex_executor.tcc
@@ -335,6 +335,54 @@ namespace __detail
	  _M_states._M_queue(__state._M_next, _M_cur_results);
    }

+  template<typename _BiIter, typename _TraitsT>
+    struct _Backref_matcher
+    {
+      _Backref_matcher(bool __icase, const _TraitsT& __traits)
+      : _M_traits(__traits) { }
+
+      bool
+      _M_apply(_BiIter __expected_begin,
+	       _BiIter __expected_end, _BiIter __actual_begin,
+	       _BiIter __actual_end)
+      {
+	return _M_traits.transform(__expected_begin, __expected_end)
+	    == _M_traits.transform(__actual_begin, __actual_end);
+      }
+
+      const _TraitsT& _M_traits;
+    };
+
+  template<typename _BiIter, typename _CharT>
+    struct _Backref_matcher<_BiIter, std::regex_traits<_CharT>>
+    {
+      using _TraitsT = std::regex_traits<_CharT>;
+      _Backref_matcher(bool __icase, const _TraitsT& __traits)
+      : _M_icase(__icase), _M_traits(__traits) { }
+
+      bool
+      _M_apply(_BiIter __expected_begin,
+	       _BiIter __expected_end, _BiIter __actual_begin,
+	       _BiIter __actual_end)
+      {
+	if (!_M_icase)
+	  return std::equal(__expected_begin, __expected_end,
+			    __actual_begin, __actual_end);

This is only valid in C++14 and higher, because the 4-argument version
of std::equal isn't present in C++11.

+	typedef std::ctype<_CharT> __ctype_type;
+	const auto& __fctyp = use_facet<__ctype_type>(_M_traits.getloc());
+	return std::equal(__expected_begin, __expected_end,
+			  __actual_begin, __actual_end,

Same here.

+			  [this, &__fctyp](_CharT __lhs, _CharT __rhs)
+			  {
+			    return __fctyp.tolower(__lhs)
+				== __fctyp.tolower(__rhs);
+			  });

We need to rewrite this to check the lengths are equal first, and then
call the 3-argument version of std::equal.

Alternatively, we could move the implementation of the C++14
std::equal overloads to __equal and make that available for C++11.
I'll try that.



Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]