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POstd::map compare function and NULL
 

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  1. POstd::map compare function and NULL
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    <p>I've written a compare function for a std::map so I can have custom key types.</p> <pre><code>std::map&lt;GGString *, GGObject *, GGDictionaryMapCompare&gt; _map; </code></pre> <p>...</p> <pre><code>class GGDictionaryMapCompare { public: bool operator()(GGString * lhs, GGString * rhs) { return strcmp(lhs-&gt;str(), rhs-&gt;str()) &lt; 0; } }; </code></pre> <p>Code that adds elements:</p> <pre><code>GGObject *GGDictionary::addKeyObject(GGString *theKey, GGObject *theObject) { if (theKey == NULL || theObject == NULL) return NULL; _map.insert(std::pair&lt;GGString *, GGObject *&gt;(theKey, theObject)); return theObject; } </code></pre> <p>Code that is causing the crash:</p> <pre><code>GGObject *GGDictionary::objectForKey(GGString *theKey) { if (theKey == NULL) return NULL; std::map&lt;GGString *, GGObject *, GGDictionaryMapCompare&gt;::iterator ii = _map.find(theKey); if (ii == _map.end()) return NULL; return GGAutoRelease(ii-&gt;second); } </code></pre> <p>Stack trace:</p> <pre><code>#0 0x00009f15 in GGString::str() #1 0x0004a4c4 in GGDictionaryMapCompare::operator()(GGString*, GGString*) #2 0x0004a3d3 in std::_Rb_tree&lt;GGString*, std::pair&lt;GGString* const, GGObject*&gt;, std::_Select1st&lt;std::pair&lt;GGString* const, GGObject*&gt; &gt;, GGDictionaryMapCompare, std::allocator&lt;std::pair&lt;GGString* const, GGObject*&gt; &gt; &gt;::find(GGString* const&amp;) #3 0x00049b04 in std::map&lt;GGString*, GGObject*, GGDictionaryMapCompare, std::allocator&lt;std::pair&lt;GGString* const, GGObject*&gt; &gt; &gt;::find(GGString* const&amp;) #4 0x00048ec9 in GGDictionary::objectForKey(GGString*) </code></pre> <p>The issue is that the lhs is coming in NULL. I never insert a NULL into the map, so this should not be happening. Any idea why? Or am I just doing the compare function wrong? I can protect against getting NULL, but it seems like something is wrong and I don't want to cure a symptom and not the problem.</p> <p>Thanks</p>
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    1. USRoger Gilbrat
    1. USRoger Gilbrat
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    1. COShow where do you add elements.
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      1. USimreal
    2. COCould you post some code about how you're using this, and/or how you're adding elements to the map? I could try to reproduce the problem. I don't see any obvious issues with that code so perhaps it's something weird in the implementation.
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      1. USMichael Oliver
    3. COIf you GGString is coming in `NULL` its the insertion of a `NULL` *key* you're looking for, NOT a `NULL` *value*
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      1. USMike Vine
 

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