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POLinux Segmentation fault with std::string::iterator
 

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  1. POLinux Segmentation fault with std::string::iterator
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    <p>I keep getting unusual segmentation faults inside libc.so.6 on a CentOS 6.4 64bit machine. This is the backtrace that gdb most often reports:</p> <pre><code>0x00007ffff60d9b3f in memcpy () from /lib64/libc.so.6 (gdb) backtrace #0 0x00007ffff60d9b3f in memcpy () from /lib64/libc.so.6 #1 0x00000000004b6a6b in std::string::_S_construct&lt;__gnu_cxx::__normal_iterator&lt;char*, std::string&gt; &gt; () #2 0x00000000004b719b in NewsMAIL::SMTPClient::receiveLine(std::basic_string&lt;char, std::char_traits&lt;char&gt;, std::allocator&lt;char&gt; &gt;*) () #3 0x00000000004b776f in NewsMAIL::SMTPClient::handleResponse() () </code></pre> <p>And this is the code in question that seems to trigger the segfault:</p> <pre><code>bool SMTPClient::receiveLine(std::string* Line) { static std::string Buffer; std::string::iterator iter; while((iter = std::find(Buffer.begin(), Buffer.end(), '\n')) == Buffer.end()) { char Bucket[MAX_BUCKET_SIZE + 1] = {}; int BytesRecv = read(m_Socket, Bucket, MAX_BUCKET_SIZE); //Did we get a socket error? if(BytesRecv == -1) { //This is generally considered a bad thing.. *Line = Buffer; Buffer = std::string(""); return false; } Bucket[BytesRecv] = 0; Buffer += Bucket; } *Line = std::string(Buffer.begin(), iter); Buffer = std::string(iter + 1, Buffer.end()); return true; } </code></pre> <p>Sometimes it works 100% without any failures so it is not everytime unfortunately. The above code is a slightly modified version of this: <a href="https://stackoverflow.com/a/1584620/3133245">https://stackoverflow.com/a/1584620/3133245</a></p> <p>Does anyone have any thoughts on why this might be happening? I am compiling with g++ 4.7.2</p> <p>Thanks!</p> <p>Nate</p>
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    1. USNate Strandberg
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    1. COIn addition to the two answers you have, the `operator+=` for strings can invalidate any iterators. Imagine this could happen if the string's internal buffer needed to be resized.
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      1. POLinux Segmentation fault with std::string::iterator
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