[RFC] Fixing the fstream problem

[Paolo Carlini <pcarlini at unitus dot it>]

Hi,

I have debugged this quite a bit and the problem seems to be that close() may
fail without a real reason. In my understanding the culprit is the following
line #185 of fstream.tcc (basic_filebuf::close()):

   if (__testput
       && _M_really_overflow(traits_type::eof()) != traits_type::eof())

Whenever __testput is false the if body is not executed at all, whereas, before
the 8th of January, the various finalizing operations were all carried out, only
_M_really_overflow was not called.

Therefore, naturally, I have prepared the following patch, which however is
still *not* complete, since there is a regression in the assertion at line #355
of filebuf.cc: for some reason sungetc does not work perfectly anymore :-(

Thoughts?

Cheers,
Paolo.

//////////////

diff -urN libstdc++-v3-curr/include/bits/fstream.tcc
libstdc++-v3/include/bits/fstream.tcc
--- libstdc++-v3-curr/include/bits/fstream.tcc Tue Jan  8 20:57:00 2002
+++ libstdc++-v3/include/bits/fstream.tcc Sat Jan 26 22:27:36 2002
@@ -182,8 +182,8 @@
       if (this->is_open())
  {
    bool __testput = _M_out_cur && _M_out_beg < _M_out_end;
-   if (__testput
-       && _M_really_overflow(traits_type::eof()) != traits_type::eof())
+   if (!__testput ||
+       _M_really_overflow(traits_type::eof()) != traits_type::eof())
      {
        // NB: Do this here so that re-opened filebufs will be cool...
        _M_mode = ios_base::openmode(0);
diff -urN libstdc++-v3-curr/testsuite/27_io/filebuf_members.cc
libstdc++-v3/testsuite/27_io/filebuf_members.cc
--- libstdc++-v3-curr/testsuite/27_io/filebuf_members.cc Tue Jan  8 20:57:01
2002
+++ libstdc++-v3/testsuite/27_io/filebuf_members.cc Sat Jan 26 19:33:23 2002
@@ -154,6 +154,29 @@
   exit(0);
 }

+// Charles Leggett <CGLeggett@lbl.gov>
+int
+test_04()
+{
+  bool test = true;
+
+  std::fstream scratch_file;
+
+  scratch_file.open("SCRATCH", std::ios::out);
+  scratch_file.close();
+
+  scratch_file.open("SCRATCH", std::ios::in);
+  scratch_file.close();
+
+  VERIFY(scratch_file);
+
+#ifdef DEBUG_ASSERT
+  assert(test);
+#endif
+
+  return test;
+}
+
 int
 main()
 {
@@ -161,5 +184,7 @@
   test_02();

   test_03();
+  test_04();
+
   return 0;
 }