[Octave-bug-tracker] [bug #62723] sscanf returns an error when there is no error

[Rik]

Follow-up Comment #8, bug #62723 (project octave):

> Additionally, I stumbled across some probably older code (maybe from when
`error` didn't throw an exception immediately). I moved the clean-up code to
before throwing the exception here:
> https://hg.savannah.gnu.org/hgweb/octave/rev/2a12350f9410

This actually won't have any effect.  I've never been happy with this, but the
octave_stream class has it's own error() function which is not the global
error function that Octave uses elsewhere.  I made a comment about this at the
top of oct-stream.cc a long time ago because I too was very confused about
this.  The comment is:


// Programming Note: There are two very different error functions used
// in the stream code.  When invoked with "error (...)" the member
// function from stream or base_stream is called.  This
// function sets the error state on the stream AND returns control to
// the caller.  The caller must then return a value at the end of the
// function.  When invoked with "::error (...)" the exception-based
// error function from error.h is used.  This function will throw an
// exception and not return control to the caller.  BE CAREFUL and
// invoke the correct error function!


The change you made


+                        is.clear (is.rdstate () & (~std::ios::failbit));
                         error (who, "format failed to match");
-                        is.clear (is.rdstate () & (~std::ios::failbit));


is still probably a good idea because anyone who is familiar with Octave is
likely to have the same confusion.  Putting the is.clear call first works
whichever version of error() is called.




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