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POStrange problems with new/delete in an app that uses my DLL
 

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  1. POStrange problems with new/delete in an app that uses my DLL
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    <p>sorry for the cryptic question title. I'm having a strange problem and i have no idea why it is happening. Fortunately, the code involved is pretty simple. But beofre we get to it, let me briefly describe my app. It is a multithreaded app that serves a large amount of data. Something like an in-ram database. It is possible to have multiple "databases" in it and load/unload them at runtime. Now the problem is with the memory deallocation. Please see the code bellow (names of classes etc are changed, but this should not matter):</p> <pre><code>void SS::AllocTree( double*** pba, int i, int d, int b, int split ) { this-&gt;m_tree = new my_tree( pba, i, d, b, split ); } void SS::DeallocTree() { delete this-&gt;m_tree; this-&gt;m_tree = NULL; } </code></pre> <p>Every time <code>delete this-&gt;m_tree</code> is called, the program crashes. The stack trace looks like this:</p> <pre><code> mydll.dll!_free_base(void * pBlock=0x0000000008496f70) Line 109 + 0x14 bytes C mydll.dll!_free_dbg_nolock(void * pUserData=0x0000000008496fa0, int nBlockUse=0x00000001) Line 1428 C++ mydll.dll!_free_dbg(void * pUserData=0x0000000008496fa0, int nBlockUse=0x00000001) Line 1258 + 0xe bytes C++ mydll.dll!operator delete(void * pUserData=0x0000000008496fa0) Line 54 + 0x12 bytes C++ mydll.dll!my_tree::`vector deleting destructor'() + 0x94 bytes C++ myprog.exe!SS::DeallocTree() Line 57 + 0x34 bytes C++ myprog.exe!SSUnloader(void * arg=0x00000000084d6f80) Line 1038 C++ msvcr90d.dll!_callthreadstart() Line 295 C msvcr90d.dll!_threadstart(void * ptd=0x00000000084dad30) Line 277 C </code></pre> <p>Here is the stack trace for the allocation of the tree:</p> <pre><code> msvcr90d.dll!malloc(unsigned __int64 nSize=0x0000000000000058) Line 56 + 0x21 bytes C++ msvcr90d.dll!operator new(unsigned __int64 size=0x0000000000000058) Line 59 + 0xa bytes C++ myprog.exe!SS::AllocTree(double * * * pba=0x0000000008458ff0, int i=0x00000bde, int d=0x00000010, int b=0x00000008, int split=0x00000001) Line 52 + 0xa bytes C++ myprog.exe!SSLoader(void * arg=0x000000000843cf80) Line 932 C++ msvcr90d.dll!_callthreadstart() Line 295 C msvcr90d.dll!_threadstart(void * ptd=0x0000000008440d30) Line 277 C </code></pre> <p>As you can see the loading/unloading is done by a separate thread specifically created for this task. Nothe that i do not use any fancy things, no custom heaps or anything, no custom operator new/delete in my dll or my program. I have no idea why does the program go into my dll and call delete there but with new, this does not happen. If I change the <code>DeallocTree()</code> to look like this:</p> <pre><code>void SS::DeallocTree() { ::operator delete( this-&gt;m_tree ); this-&gt;m_tree = NULL; } </code></pre> <p>Then everything works fine. However, i am not sure if this is correct. Shouldnt i do something similar for operator new? And how can i be sure this same problem does not occur anywhere else? For completness sake i am also attaching the stack trace for this version of DeallocTree():</p> <pre><code> msvcr90d.dll!operator delete(void * pUserData=0x00000000086f5fa0) Line 45 + 0xa bytes C++ myprog.exe!SS::DeallocTree() Line 58 C++ myprog.exe!SSUnloader(void * arg=0x0000000008735f80) Line 1038 C++ msvcr90d.dll!_callthreadstart() Line 295 C msvcr90d.dll!_threadstart(void * ptd=0x0000000008739d30) Line 277 C </code></pre> <p>Can someone explain to me what is going on here?</p> <p><strong>EDIT:</strong> <br /> To clarify:<br /> my.dll is loaded dynamically - VS 2008 output: myprog.exe': Loaded 'C:*<strong>\Debug\mydll.dll', Symbols loaded.<br /> Note: i am correctly using debug version of the dll with debug version of my program and vice versa with release.<br /> **my_tree is declared as:</strong> my_tree* m_tree; // the tree</p>
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