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List:       taglib-devel
Subject:    Re: cstring returning invalid encoding? mp3's
From:       Michael Pyne <mpyne () purinchu ! net>
Date:       2009-09-23 0:46:29
Message-ID: 200909222046.35867.mpyne () purinchu ! net
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On Tuesday 22 September 2009 07:18:07 rengels wrote:
> On Tuesday 22 September 2009 01:55:49 am ext Caleb Cushing wrote:
> > figured it out 20-ish minutes ago... memory corruption. apparently the
> > memory was popping off the stack before the pointer was assigned (or
> > something like that).  using an intermediate variable.
> > 
> > 
> > TagLib::String s( tfile.tag()->title() );
> > const char *ttitle = s.toCString(true);
> > 
> > has solved this issue.
> 
> Hi Caleb,
> it should not do that.
> As tfile does not run out of scope tag and tag->title should also remain
> valid. Strange...

tfile was not the issue, it was a temporary String returned by tfile.tag()-
> title().

Look at the API docs: 
http://developer.kde.org/~wheeler/taglib/api/classTagLib_1_1String.html#ac86b42f97707048978f4ac9dd801959


"This string remains valid until the String instance is destroyed or \
another  export method is called."

With tfile.tag()->title().toCString(true);, the temporary String returned \
by  title() is destroyed essentially as soon as that semicolon is \
encountered,  leaving the memory pointed to by ttitle in an undefined \
state.  Forcing the  String to stay alive by storing it in a local variable \
also keeps the ttitle  pointer valid.

Regards,
 - Michael Pyne


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