[Octave-bug-tracker] [bug #58055] ftell() incorrect on MS Windows platforms if file is not encoded with CRLF line endings

[John W. Eaton]

Follow-up Comment #19, bug #58055 (project octave):

Markus: thanks for finding the visual studio bug info.

Until the problem is fixed, I think a reasonable solution for us is to call
"setvbuf (FID, _IONBF, 0, 0)" on Windows systems when opening files in text
mode.  Maybe we could also create a simple test to run when Octave first needs
to do this that could determine whether the workaround is needed.  Then we
would only do this when we detect the problem.  But for now, I propose the
following simpler change:


diff --git a/libinterp/corefcn/file-io.cc b/libinterp/corefcn/file-io.cc
--- a/libinterp/corefcn/file-io.cc
+++ b/libinterp/corefcn/file-io.cc
@@ -449,6 +449,15 @@ do_stream_open (const std::string& name,
         {
           FILE *fptr = octave::sys::fopen (fname.c_str (), mode.c_str ());
 
+#if defined (__WIN32__)
+          // FIXME: Work around fseek/ftell bug on Windows systems.  See
+          // Octave bug #58055.  This should really be enabled only if
+          // fseek/ftell require setting _IONBF to work properly.
+
+          if (mode.find ('t') != std::string::npos)
+            ::setvbuf (fptr, NULL, _IONBF, 0);
+#endif
+
           retval = octave_stdiostream::create (fname, fptr, md, flt_fmt,
                                                encoding);



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