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    <p><strong>Solution</strong></p> <p>Change this line:</p> <pre><code>xml_header[xml_level] = strtok (buffer, " "); </code></pre> <p>to</p> <pre><code>xml_header[xml_level] = strdup (strtok(buffer, " ")); </code></pre> <p>And remember to free xml_headers when your program exit. </p> <p><strong>[UPDATE]</strong> Of course, you also need to check possible corner cases such as <code>strtok</code> returns <code>NULL</code>, etc...</p> <p><strong>Explanation</strong></p> <p><code>strtok</code> won't allocate extra storage for the returned tokens. My personal suspect is that it will subsititute the delimiters with <code>\0</code> <strong>in place</strong> and return you the pointer to the start of next token every time.</p> <p>Note that in your code, you allocate 256 bytes of buffer both in <code>xmlopen</code> and <code>xmlwrite</code> at the beginning, and recall that this buffer will be allocated in stack. So in your calls to <code>xmlopen</code> or <code>xmlwrite</code>, <code>buffer</code> will actually point to the same address (you can print its value to verify this <code>printf("buffer is %p\n", buffer)</code>, it's <code>0xbff2481c</code> on my machine).</p> <p>First, you call <code>xmlopen("Hello World")</code>, and <code>xml_header[0]</code> will point to <code>"Hello"</code>, which is also the start of <code>buffer</code>. Then you call <code>xmlopen("Foo Bar")</code>, and <code>xml_header[1]</code> will point to <code>"Foo"</code>, which also the start of <code>buffer</code>. Then you call <code>xmlwrite("Portato")</code> and <code>xmlwrite("Sentence longer than the other ones")</code>. Note that at this point, <code>xml_header[1]</code> still point to the start of <code>buffer</code>, which now is <code>"Sentence longer than the other ones"</code>. So when you call <code>xmlclose()</code>, it will print out that sentence instead of your expected token, which is overwrite by your later buffer.</p> <p>Interestingly, if you allocate different buffer size in <code>xmlopen</code> and <code>xmlwrite</code>, say 256 bytes for <code>xmlopen</code> and 128 bytes for <code>xmlwrite</code>, then you will see that <code>xmlclose</code> will print out some mess codes which is not readable. </p> <p>You can verify all these by inspect (e.g., print) the values of <code>xml_header[0], xml_header[1]</code> and <code>buffer</code>.</p>
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    1. CONote that strdup will fail if strtok returns NULL.
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    2. CO@PaulR: Thanks for your reminder! Error checking is absolutely needed. I just omit them here for emphasizing on the problem itself. I've updated my post accordingly.
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