How to format like "const char * fmt, ..."

[gakki2019]

Hi,
I want to make a library(linux), and export several C APIs, one of the API will be:

class logger {
public:
     std::shared_ptr<spdlog::logger> m_logger;
 }

static logger theLogger;

extern "C" void mylog_print(int lv, const char* fmt, ...) {
     // how to use spdlog::logger* pointer to handle this ?
     theLogger.m_logger->log(...);
}

invoke:
mylog_print(spdlog::level::debug, "hello {}", "spdlog");
mylog_print(spdlog::level::debug, "hello 1+1 = {}", 2);

[tt4g]

It is not possible to export C++ templates as C APIs, because the APIs are not compatible.

EDIT: C++ templates are treated like regular functions if they are specialized, so you can call them from C if you have explicit specialization: c++ - How to export template function? - Stack Overflow
But perhaps that is not what you want to do.