CODEWITHSUNDEEP
c++
JazzyBelle
JazzyBelle

Reputation: 27

segmentation fault with pointer in for loop

The code compiles fine and runs fine until the for loop to iterate through f_read_Prediction_Set. The segmentation fault occurs directly after that line...what am I missing?

std::map< RAddr, uint32_t >* transCoherence::getCurrentSets(uint32_t log2AddrLs, uint32_t maskSets, uint32_t log2Assoc, int pid, RAddr caddr)//function to return prediction set
{
   uint32_t set;
   std::map< RAddr, uint32_t >* currentSets = new std::map< RAddr, uint32_t >;
   std::map< RAddr, uint32_t >* f_read_Prediction_Set = new std::map< RAddr, uint32_t >;

   for(std::map<RAddr, uint32_t>::iterator it = f_read_Prediction_Set->begin(); it!=f_read_Prediction_Set->end(); ++it)
   {
      set = (((it->first) >> log2AddrLs) & maskSets) << log2Assoc;
      if(set == caddr)
         (*currentSets)[set] = 1;
   }

   return currentSets;
}

Upvotes: 1

Views: 386

Answers (1)

Shoe
Shoe

Reputation: 76240

Let me take your code full of pointers and dynamically allocation and translate it to an error and memory leak free version:

std::map<RAddr, uint32_t> transCoherence::getCurrentSets(uint32_t log2AddrLs, uint32_t maskSets, uint32_t log2Assoc, int pid, RAddr caddr) 
{
    std::map<RAddr, uint32_t> currentSets;
    std::map<RAddr, uint32_t> f_read_Prediction_Set;

    // populate f_read_Prediction_Set

    for (const auto& p : f_read_Prediction_Set) {
        uint32_t set = (((p.first >> log2AddrLs) & maskSets) << log2Assoc);
        if(set == caddr)
            currentSets[set] = 1;
    }

    return currentSets;
}

so that you can forget about the pointer problem entirely.

If you worried about performance you should note that there's a little thing in C++ called RVO (Return Value Optimization) that will avoid actually copying the vector back when the function returns.

Also I can't fail to notice that you use the word "set" in your map object's names, so it's good for you to know that there's an std::set class for you to use if you desire unique keys.

Upvotes: 1

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