patch: fstreams should check results of close()

[Phil Edwards <pedwards at disaster dot jaj dot com>]

libstdc++/2913

    http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view&pr=2913&database=gcc

deals with fstream not setting failbit when close() is explicitly called,
but the close fails.  I have a patch which fixes this for the cstdio=stdio
case (no clue about cstdio=libio).

There's no way I can think of to write a testsuite entry for this; how
do we /force/ a call to, say, ofstream::close() to fail?  I tested it
by playing mean games with file descriptors, but that wouldn't work in
the testsuite.  The original test case of writing to a full filesystem
got somewhat reproduced on a full floppy, but the fact is that we don't
check for problems while closing a file, and we should.

The PR submitter feels that it's a regression from 2.95, and I agree.

Thoughts?



2001-10-10  Phil Edwards  <pme@gcc.gnu.org>

	* config/io/basic_file_stdio.h (__basic_file::~__basic_file):  Don't
	bother calling fflush(), it happens automatically later.
	(__basic_file::is_open):  Make it clear we're doing pointer compares.
	(__basic_file::close):  Check fclose() return value explicitly.  Set
	_M_cfile to NULL on failure so that is_open() returns false.
	* include/bits/fstream.tcc (basic_filebuf::close):  Call _M_file->
	close() and check return value before deleting.


Index: config/io/basic_file_stdio.h
===================================================================
retrieving revision 1.1
diff -u -3 -p -r1.1 basic_file_stdio.h
--- config/io/basic_file_stdio.h	8 Aug 2001 02:48:58 -0000	1.1
+++ config/io/basic_file_stdio.h	10 Oct 2001 20:14:38 -0000
@@ -42,10 +42,7 @@ namespace std 
     __basic_file<_CharT>::~__basic_file()
     {
       if (this->is_open())
-	{
-	  fflush(_M_cfile);
 	  this->close();
-	}
     }
       
   template<typename _CharT>
@@ -131,15 +128,16 @@ namespace std 
   
   template<typename _CharT>
     bool 
-    __basic_file<_CharT>::is_open() { return _M_cfile != 0; }
+    __basic_file<_CharT>::is_open() { return _M_cfile != NULL; }
   
   template<typename _CharT>
     __basic_file<_CharT>* 
     __basic_file<_CharT>::close()
     { 
       __basic_file* __retval = static_cast<__basic_file*>(NULL);
-      if (_M_cfile_created && fclose(_M_cfile))
+      if (_M_cfile_created && (fclose(_M_cfile) == 0))
 	__retval = this;
+      _M_cfile = NULL;
       return __retval;
     }
  
Index: include/bits/fstream.tcc
===================================================================
retrieving revision 1.16
diff -u -3 -p -r1.16 fstream.tcc
--- include/bits/fstream.tcc	20 Jul 2001 00:09:31 -0000	1.16
+++ include/bits/fstream.tcc	10 Oct 2001 20:14:38 -0000
@@ -202,8 +202,10 @@ namespace std
 
       // Can actually allocate this file as part of an open and never
       // have it be opened.....
-      if (_M_file)
+      if (_M_file && __ret)
 	{
+	  if (!_M_file->close())
+	    __ret = NULL;
 	  delete _M_file;
 	  _M_file = NULL;
 	}