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Re: [Patch, libstdc++/63497] Avoid dereferencing invalid iterator in regex_executor


On 20/10/14 10:23 -0700, Tim Shen wrote:
Bootstrapped and tested.

Did you manage to produce a testcase that crashed on trunk?

@@ -407,25 +409,28 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
  template<typename _BiIter, typename _Alloc, typename _TraitsT,
	   bool __dfs_mode>
    bool _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>::
-    _M_word_boundary(_State<_TraitsT>) const
+    _M_word_boundary(_State<_TraitsT>)
    {
-      // By definition.
-      bool __ans = false;
-      auto __pre = _M_current;
-      --__pre;
-      if (!(_M_at_begin() && _M_at_end()))
+      bool __left_is_word = false;
+      if (_M_current != _M_begin
+	  || (_M_flags & regex_constants::match_prev_avail))
	{
-	  if (_M_at_begin())
-	    __ans = _M_is_word(*_M_current)
-	      && !(_M_flags & regex_constants::match_not_bow);
-	  else if (_M_at_end())
-	    __ans = _M_is_word(*__pre)
-	      && !(_M_flags & regex_constants::match_not_eow);
-	  else
-	    __ans = _M_is_word(*_M_current)
-	      != _M_is_word(*__pre);
+	  --_M_current;
+	  if (_M_is_word(*_M_current))
+	    __left_is_word = true;
+	  ++_M_current;

Is it really necessary to modify _M_current here?
Couldn't you do:

      auto __pre = _M_current;
      if (_M_is_word(*--__pre))
        __left_is_word = true;

Then the function could remain const, couldn't it?


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