I am writing some data loader libraries and I am sticking to standard libraries to make them as portable as possible, just in-case we want to utilize the loaders outside of a Qt environment. I am building a std::string with the file header information in a function called string DataType::getHeaderString( ).

Qt Code: 
  1. string DataType::getHeaderString( )
  2. {
  3.    ostringstream collection,
  4.                       segment,
  5.                      altitude,
  6.                      longitude,
  7.                     latitude;
  8.  
  9.    string hdr;
  10.  
  11.    hdr += string("Timestamp: ") + mTimestamp + string("\n");
  12.  
  13.    hdr += string("Description: ") + mDesc + string("\n");
  14.  
  15.    collection << mCollectionNumber;
  16.    hdr += string("Collection Number: ") + collection.str( ) + string("\n");
  17.  
  18.    segment << mSegmentNumber;
  19.    hdr += string("Segment Number: ") + segment.str( ) + string("\n");
  20.  
  21.    altitude << mLocation.altitude;
  22.    hdr += string("Location:\n   Altitude: ") + altitude.str( ) + string("\n");
  23.  
  24.    latitude << mLocation.latitude;
  25.    hdr += string("   Latitude: ") + latitude.str( ) + string("\n");
  26.  
  27.    longitude << mLocation.longitude;
  28.    hdr += string("   Longitude: ") + longitude.str( ) + string("\n");
  29.  
  30.    hdr += string("Data Type: ") + mDataType + string("\n");
  31.  
  32.    return hdr;
  33. }
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Immediatly after calling this function
Qt Code: 
  1. string hdrStr( data.getHeaderString( ) );
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, Visual Studios 2003 returns a "Invalid Heap Pointer" exception and aborts. I was reading in forums to pass the string as a reference argument:
Qt Code: 
  1. void DataType::getHeaderString( string &hdr )
  2. {
  3.    ostringstream collection,
  4.                       segment,
  5.                      altitude,
  6.                      longitude,
  7.                     latitude;
  8.  
  9.    hdr += string("Timestamp: ") + mTimestamp + string("\n");
  10.  
  11.    hdr += string("Description: ") + mDesc + string("\n");
  12.  
  13.    collection << mCollectionNumber;
  14.    hdr += string("Collection Number: ") + collection.str( ) + string("\n");
  15.  
  16.    segment << mSegmentNumber;
  17.    hdr += string("Segment Number: ") + segment.str( ) + string("\n");
  18.  
  19.    altitude << mLocation.altitude;
  20.    hdr += string("Location:\n   Altitude: ") + altitude.str( ) + string("\n");
  21.  
  22.    latitude << mLocation.latitude;
  23.    hdr += string("   Latitude: ") + latitude.str( ) + string("\n");
  24.  
  25.    longitude << mLocation.longitude;
  26.    hdr += string("   Longitude: ") + longitude.str( ) + string("\n");
  27.  
  28.    hdr += string("Data Type: ") + mDataType + string("\n");
  29.  
  30.    return hdr;
  31. }
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but I receive the same error when I reach the end of the scope of the string.

Qt Code: 
  1. {
  2.    string hdrStr;
  3.  
  4.    data.getHeaderString( hdrString );
  5. } // Error occurs after brace
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I am really at a loss as to why this is occuring. I have used strings before in this fashion on Linux and VS 6.0 without any problems. Any suggestions?

Thanks!