C ++: How can I solve the exception from the first chance, caused in an unknown place?

Question

The C ++ project I'm working on ends when the first chance exception is thrown. This happens in Visual Studio 2008 in debug mode, when I first try to access a map<pair<int,int>, int> , which contains one key-value pair. There is nothing logical in the code.

I read about the exceptions of the first chance and understand that they may not always be problematic. However, I tried to break all such exceptions, and as expected, several were generated that did not cause a problem.

The class I'm working on is very large and contains many custom memory allocations. I guess for some reason one of them is causing a problem. However, I spent several hours trying to find a way to determine what was going wrong and could not do it.

Below is a list of exception exceptions for the first chance. This is not very helpful!

 First-chance exception at 0x762cd09c in theapp.exe: 0xC0000005: Access violation reading location 0x6c696d00. First-chance exception at 0x762cd09c in theapp.exe: 0xC0000005: Access violation reading location 0x6c696d00. First-chance exception at 0x762cd09c in theapp.exe: 0xC0000005: Access violation reading location 0x6c696d00. First-chance exception at 0x762cd09c in theapp.exe: 0xC0000005: Access violation reading location 0x6c696d00. First-chance exception at 0x762cd09c in theapp.exe: 0xC0000005: Access violation reading location 0x6c696d00. First-chance exception at 0x762cd09c in theapp.exe: 0xC0000005: Access violation reading location 0x6c696d00. First-chance exception at 0x762cd09c in theapp.exe: 0xC0000005: Access violation reading location 0x6c696d00. First-chance exception at 0x762cd09c in theapp.exe: 0xC0000005: Access violation reading location 0x6c696d00. First-chance exception at 0x762cd09c in theapp.exe: 0xC0000005: Access violation reading location 0x6c696d00. First-chance exception at 0x762cd09c in theapp.exe: 0xC0000005: Access violation reading location 0x6c696d00. First-chance exception at 0x762cd09c in theapp.exe: 0xC0000005: Access violation reading location 0x6c696d00. First-chance exception at 0x762cd09c in theapp.exe: 0xC0000005: Access violation reading location 0x6c696d00. First-chance exception at 0x762cd09c in theapp.exe: 0xC0000005: Access violation reading location 0x6c696d00. First-chance exception at 0x762cd09c in theapp.exe: 0xC0000005: Access violation reading location 0x6c696d00. First-chance exception at 0x762cd09c in theapp.exe: 0xC0000005: Access violation reading location 0x6c696d00. First-chance exception at 0x0050ae33 in theapp.exe: 0xC0000005: Access violation reading location 0x00000010. Unhandled exception at 0x0050ae33 in theapp.exe: 0xC0000005: Access violation reading location 0x00000010. 

I am really afraid at this moment and do not know how to do it.

Can anyone suggest how I can solve this problem and pinpoint what is happening? I would be very grateful for your advice.

UPDATE

Here is the relevant code. The debugger breaks into the first cout statement specified in the nested FOR:

  // Inside operator() : map<pair<int,int>,int> resultIdByStructIds; pair<int,int> spair (-1,-1); // Structure pair ids reusable reference. int nextMapEntryId = 0; int nextNumCandidates = 0; // For each remaining candidate. for (int ci = 0; ci < numCandidates; ) { // If candidate has been mapped or found not viable this mapping round, // move past it. if (candidatesDoneThisRound[ci] == currentMappingRoundId) { ++ci; continue; } Candidate candidate = candidates[ci]; const int tId = candidate.tVertexId; const int pId = candidate.pVertexId; // Grab the result for this structure pair. // Create it if it doesn't exist. // Avoid copying as slight optimisation; simply // store pointer to true result instead. spair.first = tInfos[tId].structure->id; spair.second = pInfos[pId].structure->id; // DEBUG cout << "resultIdByStructIds size: " << resultIdByStructIds.size() << endl; for (map<pair<int,int>,int>::const_iterator ids_id = resultIdByStructIds.begin(); ids_id != resultIdByStructIds.end(); ++ids_id) { cout << ids_id->first.first << endl; // * Debugger breaks here. cout << ids_id->first.second << endl; cout << ids_id->second << endl; printf("Structures(%i,%i) => %i\n",ids_id->first.first,ids_id->first.second,ids_id->second); } // // code continues... 

UPDATE 2

Here is a description of the mouse for the map in question; he seems distorted, as Michael Burr suggested.

Answer 1

In general, to pinpoint where the application crashes, you can enable exception handling in the Debug / Exceptions section. In this case, you should expand the last branch and check the access violation. Of course, this will stop all access violations, and not just bad ones (access to 0x10). You can minimize this by turning on the trap at the last known moment.

You will usually find a memory usage error. The easiest way to determine the cause of this type of error is with a third-party tool, such as BoundChecker, that will scream at you as soon as you corrupt your memory. Not having this, Raymond Chen advises. Find out which object is wrong, and use the viewport to see when it changed. Or it’s more efficient to use the “Data Breakpoint” function so that the program stops when data changes at a specific address.