ThorsSQL Lib Utility

Question

These are some utility functions that I use for building error messages:

SQLUtil.h

#ifndef THORS_ANVIL_SQL_SQL_UTIL_H
#define THORS_ANVIL_SQL_SQL_UTIL_H
#include <map>
#include <string>
#include <sstream>
namespace ThorsAnvil
{
 namespace SQL
 {
using Options=std::map<std::string, std::string>;
 }
/* The following is generic to all ThorsAnvil Code */
/* Build error message or bug report for exceptions */
template<typename T>
void printItem(std::ostream& str, T const& msg)
{
 str << msg;
}
template<typename... Args>
std::string stringBuild(Args const& ...a)
{
 std::stringstream msg;
 auto list = {0, (printItem(msg, a), 0) ...};
 (void)list;
 return msg.str();
}
template<typename... Args>
std::string errorMsg(Args const& ...a)
{
 return stringBuild(a...);
}
template<typename... Args>
std::string bugReport(Args const& ...a)
{
 return stringBuild(a..., "\nPlease File a Bug Report: ");
}
}
#endif

Answer 1

The ThorsAnvil::SQL::Options type is defined, but never used, so it's hard to say much about it.

---

That's a clever way to get around the lack of fold-expressions in C++14:

auto list = {0, (printItem(msg, a), 0) ...};
(void)list;

I would probably use a version conditional, to show the intent before the workaround:

#if __cplusplus >= 201703L
 (msg << ... << a);
#else
 auto list = {0, (printItem(msg, a), 0) ...};
 (void)list;
#endif