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POWhat does new [size_t] + 1 return
 

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  1. POWhat does new [size_t] + 1 return
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    <p>The following sample of code if from a book "C++ von A bis Z" (second edition, translation: C++ from A to Z) at page 364. The sample is wrong.</p> <pre><code>// overload operator += #include &lt;iostream&gt; #include &lt;cstring&gt; using namespace std; class String { private: char* buffer; unsigned int len; public: String(const char* s="") { // cout &lt;&lt; "Constructor: " &lt;&lt; s &lt;&lt; "\n"; len = strlen(s); buffer = new char [len+1]; strcpy(buffer, s); } ~String() { // cout &lt;&lt; "Destructor: " &lt;&lt; buffer &lt;&lt; "\n"; delete [] buffer; } String(const String&amp; s) { // cout &lt;&lt; "Copy_Constructor: " &lt;&lt; s.get_buffer() &lt;&lt; "\n"; len = s.len; buffer = new char [len+1]; strcpy(buffer, s.buffer); } char* get_buffer() const { return buffer; } // returning a reference is more efficent // String&amp; operater+=(const String&amp; str1) String operator+=(const String&amp; str1) { // cout &lt;&lt; "Assignment_Operator +=: " &lt;&lt; str1.get_buffer() &lt;&lt; "\n"; String tmp(*this); delete [] buffer; len = tmp.len + str1.len; // invalid pointer // buffer = new char[len+1]; buffer = new char [len]+1; strcpy(buffer, tmp.buffer); strcat(buffer, str1.buffer); // wrong return_type // return *this; return buffer; } }; int main(void) { String string1("Adam"); String string2("Eva"); string1+=" und "; string1.operator+=(string2); cout &lt;&lt; string1.get_buffer() &lt;&lt; "\n"; return 0; } </code></pre> <p>The lines with the comments are my "fixes". Now I want to know what "new char [len]+1" does? I think the following:</p> <ul> <li>it allocates sizeof(char)*len memory from heap</li> <li>and returns the WRONG address to the pointer *buffer</li> <li>but what is the wrong address: "first address of the new memory on heap + 1" or "first address of the new memory on heap + sizeof(char)*1)?</li> </ul> <p>What happens? Thanks</p> <p>// edit Thank you all! You helped me! I just wanted to know, what this statement will return.</p> <pre><code>new char [len]+1; </code></pre> <p>The line itself is, of course, a typo from the author of the book.</p>
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    1. COHow is your third point different? `sizeof(char) == 1` by definition.
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    2. COAlso, who gives a crap -- if you're doing C++, forget about `char*` and `strcpy` and raw arrays.
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    3. COI guess you're right in all your assumptions. The returned address is "first address of the new memory on heap + sizeof(char)*1", but that makes no sense for this code anyway.
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