How to Use va_args in C

#include stdio.h>
#include stdarg.h>
void LogMsg(int lvl, char *fmt,...)
{
va_list vList ;
char msg[256] ;
char debugmsg[500] ;
printf(" Size %d\n",sizeof(debugmsg));
if(lvl ==1)
{
va_start(vList,fmt) ;
vsnprintf(msg, 256, fmt, vList) ;
sprintf(debugmsg, " %s\n", msg) ;
printf("debugmsg : %s msg : %s\n", debugmsg, msg) ;
va_end(vList);
}
}

int main()
{

printf(" \n");
LogMsg(1,"%s %d Test Message \n",__func__,__LINE__);
return 0;
}
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