c++14 - Customize the deleter to deallocate a 2D array through std::unique_ptr -

suppose parsing environment variable list given map<string, string> 2d memory held unique_ptr<char*[]>. however, not sure how can customise deleter 2d memory case ?

// given: env (type of map<string, string>) // return: unique_ptr<char*[]> (with customized deleter)  // prepare parsing environment c-style strings auto idx = size_t{0};  // should fill `ret` proper deleter won't give memory leak? auto ret = std::make_unique<char*[]>(env.size() + 1, ???);    for(const auto& kvp : env) {   auto entry = kvp.first + "=" + kvp.second;   ret[idx] = new char[entry.size() + 1];    strncpy(ret[idx], entry.c_str(), entry.size() + 1);    ++idx; } ret[idx] = nullptr;  // later use of exec call  return ret; 

apparently, above code leaks, because of new operator in inner loop.

there no version of std::make_unique accepting deleter argument (by way, std::make_unique c++14, not c++11). try this:

size_t size = env.size() + 1;  auto ret = std::unique_ptr<char*, std::function<void(char**)> >(     new char* [size],     [size](char** ptr)     {         for(size_t i(0); < size; ++i)         {             delete[] ptr[i];         }         delete[] ptr;     } ); 

you can pass ret.get() execvpe.