Detecting and fixing heap corruption in C++

I'm having an issue with heap corruption in a (win32)C++ application. After inserting _heapchk() into the code I've managed to narrow down the cause. The application runs; however it crashes "every now and then". Here is the code:

void parse_config(void) { int *regex_d; // regex data parsed fields(from a line from config_file) vector<string> input_fields; // filtered data ifstream file(param.topology_file.c_str());// open file for input ifstream reg_file(param.regex_file.c_str()); // open the regex file and read contents(all content is placed on a single line -- no new line characters allowed) if(reg_file.is_open()) { // read regex content into the string regex variable param.regex.assign((istreambuf_iterator<char>(reg_file)), istreambuf_iterator<char>()); reg_file.close(); } split_regex(); string buff; // store contents of input file string::const_iterator start, end; int temp, temp1, temp2; int n_of_fields = 0; // number of fields found in an input line const size_t l = 10; // number of digits each data field has for(unsigned i = 0; i < strlen(topology_component); i++) { if(topology_component[i] == ':') n_of_fields++; } input_fields.resize(n_of_fields); regex_d = new int[n_of_fields]; for(vector<string>::iterator iter = input_fields.begin(); iter != input_fields.end(); iter++) { (*iter).reserve(l); } if (file.is_open()) { file.seekg(0, ios::end); buff.reserve(file.tellg()); file.seekg(0, ios::beg); buff.assign((istreambuf_iterator<char>(file)), istreambuf_iterator<char>()); // read contents of file in buff file.close(); boost::regex expression(topology_component); boost::match_results<string::const_iterator> m_res; boost::match_flag_type flags = boost::match_default; start = buff.begin(); end = buff.end(); // searching the buffer for valid entries while(boost::regex_search(start, end, m_res, expression, flags)) { start = m_res[0].second; flags |= boost::match_prev_avail; flags |= boost::match_not_bob; int i = 1; for(vector<string>::iterator iter = input_fields.begin(); iter != input_fields.end(); iter++, i++) { (*iter).erase(); (*iter).append(m_res[i]); sscanf((*iter).c_str(), "%d", &regex_d[i]); } ... } n_of_fields = 0; for(unsigned i = 0; i < strlen(routing_component); i++) { if(routing_component[i] == ':') n_of_fields++; } delete[] regex_d; regex_d = NULL; input_fields.resize(n_of_fields); regex_d = new int[n_of_fields]; for(vector<string>::iterator iter = input_fields.begin(); iter != input_fields.end(); iter++) // allocate memory { iter->reserve(l); } boost::regex expression(routing_component); boost::match_results<string::const_iterator> m_res; boost::match_flag_type flags = boost::match_default; start = buff.begin(); end = buff.end(); // searching the buffer for valid entries // rtable_cur:0 rtable_dst:0 rtable_nxt:0 rtable_vc:0 while(boost::regex_search(start, end, m_res, expression, flags)) { start = m_res[0].second; flags |= boost::match_prev_avail; flags |= boost::match_not_bob; // parse one line from config file int i = 1; for(vector<string>::iterator iter = input_fields.begin(); iter != input_fields.end(); iter++, i++) { (*iter).erase(); // <== HEAP CORRUPTION OCCURS HERE (*iter).append(m_res[i]); // <== HEAP CORRUPTION sscanf((*iter).c_str(), "%d", &regex_d[i]); // <== HEAP CORRUPTION } ... } ... } 

When I attempt to reuse the input_fields vector the heap becomes and remains corrupted throughout the program. param is a container which contains validated user input. The split_regex() method is used to obtain two strings:topology_component and routing_component. Both are of type char*.

 void split_regex(void) // regex is of type "topology_component|routing_component" { bool split = false; unsigned i, j = 0; if(topology_component == NULL) { topology_component = (char*)malloc(REGEX_SIZE); } if(routing_component == NULL) { routing_component = (char*)malloc(REGEX_SIZE); } for(i = 0; i < param.regex.size(); i++) { if(split == false) { if(param.regex.at(i) == '|') { split = true; j = 0; continue; } topology_component[i] = param.regex[i]; } else { topology_component[i-1] = '\0'; routing_component[j++] = param.regex[i]; } } routing_component[j] = '\0'; }