If you encounter a linking issue with g++ like this, please use extern "C"

[GoingMyWay]

CMakeFiles/project_tlinux.dir/include/metric/prometheus.cpp.o: In function `metric::Prometheus::StartHttpServer()':                                                                                                                     
prometheus_producer.cpp:(.text+0x141): undefined reference to `promhttp_start_daemon(unsigned int, unsigned short, int (*)(void*, sockaddr const*, unsigned int), void*)'                                                                                                
CMakeFiles/project_tlinux.dir/include/metric/prometheus_producer.cpp.o: In function `metric::Prometheus::PrometheusProducer(int)':                                                                                                               
prometheus_producer.cpp:(.text+0x1af): undefined reference to `promhttp_start_daemon(unsigned int, unsigned short, int (*)(void*, sockaddr const*, unsigned int), void*)'                                                                                                
prometheus.cpp:(.text+0x1b8): undefined reference to `prom_collector_registry_default_init()'                

If you encounter a linking issue like this, please use extern "C" in this way in you C++ project:

#ifdef __cplusplus
extern "C" {
#endif

#include "promhttp.h"  // Include the original C header
#include "prom.h"      // Include the original C header

#ifdef __cplusplus
}
#endif