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list iterator not dereferencable

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Join Date: Feb 2008

Posts: 17

Reputation: Natique is an unknown quantity at this point

Solved Threads: 0

Natique

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Newbie Poster

list iterator not dereferencable

Sep 26th, 2009

The following is a function that compiles just fine, but when I run it, I get a "Debug Assertion Failed" and it says "list iterator not dereferencable". As far as I can tell the error occurs at whileIter++. I've looked at examples of iterators and how they are used, and can't figure out what I'm doing wrong.

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
CString findImage(CString fileName, list<record> csvFile)
{
	std::list<record> tmpCsvFile = csvFile;
	std::list<record>::iterator tmpIterator = tmpCsvFile.begin();
	list<record>::iterator whileIter = tmpCsvFile.begin();
fileName = fileName+".txt";
 
		while (whileIter != tmpCsvFile.end())
		{
		      whileIter++;
		if (fileName == (whileIter->fileName).c_str())
			break;
 
		}
 
return whileIter->characters.c_str();
}
CString findImage(CString fileName, list<record> csvFile)
{
	std::list<record> tmpCsvFile = csvFile;
	std::list<record>::iterator tmpIterator = tmpCsvFile.begin();
	list<record>::iterator whileIter = tmpCsvFile.begin();
fileName = fileName+".txt";
		
		while (whileIter != tmpCsvFile.end())
		{
		      whileIter++;
		if (fileName == (whileIter->fileName).c_str())
			break;
			
		}
		
return whileIter->characters.c_str();
}

Basically there is a list of records ( a struct with a few members, one of which is fileName). The function should compare the fileName in each record of the list, with the fileName that was passed as a parameter to the function in the hope of finding two that are equal.

Thanks in advance

•

Join Date: May 2008

Posts: 538

Reputation: Murtan is a jewel in the rough

Solved Threads: 86

Murtan

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Posting Pro

Re: list iterator not dereferencable

Sep 30th, 2009

Your problem is inside the while loop.

 Help with Code Tags 
 c++ Syntax (Toggle Plain Text) 
		while (whileIter != tmpCsvFile.end())
		{
		      whileIter++;
		if (fileName == (whileIter->fileName).c_str())
			break;
 
		}
		while (whileIter != tmpCsvFile.end())
		{
		      whileIter++;
		if (fileName == (whileIter->fileName).c_str())
			break;
			
		}

You have advanced the iterator (possibly to the end) before you try to test the filename. Put the fileName test (with the break) before the iterator advancement.