[Patch] Remove basic_filebuf::_M_last_overflowed

[Paolo Carlini <pcarlini at unitus dot it>]

Hi,

this was real fun!

In std_fstream.h we had this comment

   // XXX Needed?
   bool            _M_last_overflowed;

so I had a look. The only place where it was used
was seekeoff():

   // Sync the internal and external streams.
   // out
   if (__testput || _M_last_overflowed)
     {
       // Part one: update the output sequence.

And the only place where it was *apparently* set to true
was _M_overflow().

However, overflow(), just before returning, set it back
to false! And I went ahead: in all the other places where
_M_overflow() was called, before returning _M_last_overflowed
was also set back to false (*)!

Therefore, it could *never* happen that it was true in
that 'if' inside seekoff()! (QED ;)

Tested x86-linux, ok for trunk?

Paolo.

(*) And/or seekoff() was not called in the middle
(e.g., _M_underflow()).

2003-05-03  Paolo Carlini  <pcarlini@unitus.it>

	Remove basic_filebuf::_M_last_overflowed
	* include/std/std_fstream.h (~basic_filebuf(), sync()): Don't
	set _M_last_overflowed.
	* include/bits/fstream.tcc (basic_filebuf(), close(),
	showmanyc(), pbackfail(), overflow(), _M_overflow(), setbuf(),
	imbue()): Likewise.
	(seekoff): Remove from 'if' condition, don't set.
	* src/fstream.cc (basic_filebuf<char/wchar_t>::_M_underflow):
	Don't set _M_last_overflowed.

diff -urN libstdc++-v3-orig/include/bits/fstream.tcc libstdc++-v3/include/bits/fstream.tcc
--- libstdc++-v3-orig/include/bits/fstream.tcc	2003-04-29 21:46:07.000000000 +0200
+++ libstdc++-v3/include/bits/fstream.tcc	2003-05-03 13:39:32.000000000 +0200
@@ -77,8 +77,7 @@
     basic_filebuf() : __streambuf_type(), _M_file(&_M_lock), 
     _M_state_cur(__state_type()), _M_state_beg(__state_type()), 
     _M_buf(NULL), _M_buf_size(BUFSIZ), _M_buf_allocated(false),
-    _M_last_overflowed(false), _M_pback_cur_save(0),
-    _M_pback_end_save(0), _M_pback_init(false)
+    _M_pback_cur_save(0), _M_pback_end_save(0), _M_pback_init(false)
     { this->_M_buf_unified = true; }
 
   template<typename _CharT, typename _Traits>
@@ -129,7 +128,7 @@
 
 #if 0
 	      // XXX not done
-	      if (_M_last_overflowed)
+	      if (__testput)
 		{
 		  _M_output_unshift();
 		  _M_overflow(__eof);
@@ -152,7 +151,6 @@
 	  if (!__testfail)
 	    __ret = this;
 	}
-      _M_last_overflowed = false;
       return __ret;
     }
 
@@ -177,7 +175,6 @@
 	    __ret += _M_file.showmanyc_helper(__testsync) / __cvt.max_length();
 	}
 
-      _M_last_overflowed = false;	
       return __ret;
     }
   
@@ -240,7 +237,6 @@
 		}
  	    }
 	}
-      _M_last_overflowed = false;	
       return __ret;
     }
 
@@ -267,7 +263,6 @@
 	    __ret = this->_M_overflow(__c);
 	}
 
-      _M_last_overflowed = false;    // Set in _M_overflow, below.
       return __ret;
     }
   
@@ -396,7 +391,6 @@
 		}
 	    }
 	}
-      _M_last_overflowed = true;	
       return __ret;
     }
 
@@ -422,7 +416,6 @@
 	  this->_M_buf_size = __n;
 	  _M_set_indeterminate();
 	}
-      _M_last_overflowed = false;	
       return this; 
     }
   
@@ -456,7 +449,7 @@
 	      const bool __testput = this->_M_out_beg < this->_M_out_lim;
 	      // Sync the internal and external streams.
 	      // out
-	      if (__testput || _M_last_overflowed)
+	      if (__testput)
 		{
 		  // Part one: update the output sequence.
 		  this->sync();
@@ -487,7 +480,6 @@
 		}
 	    }
 	}
-      _M_last_overflowed = false;	
       return __ret;
     }
 
@@ -523,7 +515,6 @@
       // converted chars. This in turn may cause the reconstruction
       // of the original file. YIKES!!
       // XXX The part in the above comment is not done.
-      _M_last_overflowed = false;	
     }
 
   // Inhibit implicit instantiations for required instantiations,
diff -urN libstdc++-v3-orig/include/std/std_fstream.h libstdc++-v3/include/std/std_fstream.h
--- libstdc++-v3-orig/include/std/std_fstream.h	2003-04-29 01:51:36.000000000 +0200
+++ libstdc++-v3/include/std/std_fstream.h	2003-05-03 12:59:07.000000000 +0200
@@ -136,9 +136,6 @@
       */
       bool			_M_buf_allocated;
       
-      // XXX Needed?
-      bool			_M_last_overflowed;
-
       // The position in the buffer corresponding to the external file
       // pointer.
       /**
@@ -225,7 +222,6 @@
       {
 	this->close();
 	_M_buf_size = 0;
-	_M_last_overflowed = false;
       }
 
       // Members:
@@ -406,7 +402,6 @@
 	else
 	  _M_file.sync();
 
-	_M_last_overflowed = false;
 	return __ret;
       }
 
diff -urN libstdc++-v3-orig/src/fstream.cc libstdc++-v3/src/fstream.cc
--- libstdc++-v3-orig/src/fstream.cc	2003-04-28 06:54:54.000000000 +0200
+++ libstdc++-v3/src/fstream.cc	2003-05-03 12:54:36.000000000 +0200
@@ -102,7 +102,6 @@
 		}	   
 	    }
 	}
-      _M_last_overflowed = false;	
       return __ret;
     }
 
@@ -207,7 +206,6 @@
 		}	   
 	    }
 	}
-      _M_last_overflowed = false;	
       return __ret;
     }