Simple query-parameter parser in c++

main.cpp

#include <unordered_map>
#include <iostream>

// Parse URI-query parameters into a unordered_map, borrowing the input string. String must be null-terminated.
template <typename C>
std::unordered_map<std::basic_string_view<C>, std::basic_string_view<C>> parse_query_string(const C *query_string)
{
    std::unordered_map<std::basic_string_view<C>, std::basic_string_view<C>> query_map;

    if (query_string == nullptr)
    {
        return query_map;
    }

    if (*query_string == '\0')
    {
        return query_map;
    }

    const C *key = query_string + 1;
    const C *value = nullptr;
    const C *p = key;

    while (true)
    {
        if (*p == '=')
        {
            value = p + 1;
        }
        else if (*p == '&' || *p == '\0')
        {
            if (value == nullptr)
            {
                if (p - key != 0)
                {
                    query_map.emplace(std::basic_string_view<C>(key, p - key), std::basic_string_view<C>());
                }
            }
            else
            {
                query_map[std::basic_string_view<C>(key, value - key - 1)] = std::basic_string_view<C>(value, p - value);
            }

            key = p + 1;
            value = nullptr;
        }

        if (*p == '\0')
        {
            break;
        }
        else
        {
            p++;
        }
    }

    return query_map;
}

int main(int, char **, char **)
{
    const wchar_t *query_string = L"?cool4&query=hello+world&cool2&lang=en&enc=utf-8&cool=yes&cool3";
    auto query_map = parse_query_string(query_string);

    for (auto &pair : query_map)
    {
        std::wcout << pair.first << L": " << pair.second << std::endl;
    }

    return 0;
}

Makefile

CLFAGS=-std=c++17 -g -O1 -flto -fPIE -pie -Wall -Wextra -fno-omit-frame-pointer -fsanitize=address,leak,undefined
SRC=main.cpp
CXX=clang++

query-param-thing: $(SRC)
	$(CXX) $(CLFAGS) -o query-param-thing $(SRC)