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POUnexpected Non-NULL return
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  1. POUnexpected Non-NULL return
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    copied!<p>I am playing with TagLib (on Windows, built with MingW). I am trying to get TagLib to recognize when there is no ID3v1 or ID3v2 information in an MP3 file. According to the <a href="http://developer.kde.org/~wheeler/taglib/api/classTagLib_1_1MPEG_1_1File.html#ebe5029bca925e9ed7002b00244c1240" rel="nofollow">TagLib documentation</a>, the ID3v2Tag() function in an MPEG File object should return a NULL pointer when there is no ID3v2 information in the file.</p> <p>Unfortunately, this is not occurring. I have some test MP3 files I have made that I use in my code (I have made the files available):</p> <ul> <li><strong>blank.mp3</strong> (<a href="http://storage.joelverhagen.com/taglib/tests/other/blank.mp3" rel="nofollow">download</a>), no ID3v1 or ID3v2 information at all. I can confirm this by doing a plain text search for "TAG" and "ID3" in the files binary content.</li> <li><strong>only_album_id3v2.mp3</strong> (<a href="http://storage.joelverhagen.com/taglib/tests/id3v2/only_album_id3v2.mp3" rel="nofollow">download</a>), has ID3v2 information (only the album is set)</li> <li><strong>only_album_id3v1.mp3</strong> (<a href="http://storage.joelverhagen.com/taglib/tests/id3v1/only_album_id3v1.mp3" rel="nofollow">download</a>), has ID3v1 information (only the album is set)</li> </ul> <p>Here is my code.</p> <pre><code>#include &lt;iostream&gt; #include &lt;mpeg/mpegfile.h&gt; #include &lt;mpeg/id3v2/id3v2tag.h&gt; using namespace std; int main() { cout &lt;&lt; "Test." &lt;&lt; endl; TagLib::MPEG::File a("tests/other/blank.mp3"); TagLib::MPEG::File b("tests/id3v2/only_album_id3v2.mp3"); TagLib::MPEG::File c("tests/id3v1/only_album_id3v1.mp3"); TagLib::ID3v2::Tag * at = a.ID3v2Tag(); TagLib::ID3v2::Tag * bt = b.ID3v2Tag(); TagLib::ID3v2::Tag * ct = c.ID3v2Tag(); cout &lt;&lt; at-&gt;album() &lt;&lt; endl; cout &lt;&lt; bt-&gt;album() &lt;&lt; endl; cout &lt;&lt; ct-&gt;album() &lt;&lt; endl; cout &lt;&lt; "The program is done."; return 0; } </code></pre> <p>Running this program should break, due to a NULL pointer error on <code>cout &lt;&lt; at-&gt;album() &lt;&lt; endl;</code>, but it runs just fine. Also, when I <code>cout &lt;&lt; ct &lt;&lt; endl;</code>, it returns a memory address.</p> <p>Here is the output:</p> <blockquote> <p>Test.</p> <p>test album id3v2</p> <p>The program is done.</p> </blockquote> <p><strong>EDIT:</strong> Here is a new test.</p> <pre><code>#include &lt;iostream&gt; #include &lt;mpeg/mpegfile.h&gt; #include &lt;mpeg/id3v2/id3v2tag.h&gt; using namespace std; int main() { cout &lt;&lt; "Test." &lt;&lt; endl; TagLib::MPEG::File a("tests/other/blank.mp3"); TagLib::MPEG::File b("tests/id3v2/only_album_id3v2.mp3"); TagLib::MPEG::File c("tests/id3v1/only_album_id3v1.mp3"); TagLib::ID3v2::Tag * at = a.ID3v2Tag(); TagLib::ID3v2::Tag * bt = b.ID3v2Tag(); TagLib::ID3v2::Tag * ct = c.ID3v2Tag(); if(at == NULL) { cout &lt;&lt; "at is NULL."; } else { cout &lt;&lt; "at is not NULL."; } cout &lt;&lt; endl; if(bt == NULL) { cout &lt;&lt; "bt is NULL."; } else { cout &lt;&lt; "bt is not NULL."; } cout &lt;&lt; endl; if(ct == NULL) { cout &lt;&lt; "ct is NULL."; } else { cout &lt;&lt; "ct is not NULL."; } cout &lt;&lt; endl; cout &lt;&lt; "The program is done."; return 0; } </code></pre> <p>And here is the output.</p> <blockquote> <p>Test.<br> at is not NULL.<br> bt is not NULL.<br> ct is not NULL.<br> The program is done. </p> </blockquote>
 

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