I am seeing one logger method called in my project as below but I could not find exact definition anywhere.
Call:

APP_SERROR("Error appeared : " << err.message());

I however see one macro declaration as below

#define ZTP_SERROR(format ,...)
do { 
    APP_SERROR("<ZTP> " format, ##__VA_ARGS__); 
} while (0)

Here I don’t understand how this call is made as APP_SERROR instead of ZTP_SERROR. I created a sample program and tried calling both way with one string argument and compilation failed.
Dear friends, Can you please explain me this whole logic? In case if I am missing anything then can u please give me a proper method with variable number of arguments? Thanks in advance. Your small help means a lot to me.

1. I checked entire code base and did not see further definition.
2. I created a sample program to test it but compilation failed.