使用宏打印错误信息

#include <iostream>
#include <stdio.h>
#include <err.h>

using namespace std;

// Prints warning message on stderr in the format:
// <progname>: FILE:LINE in FUNC: <fmt>: <errno_msg>
#define twarn(...) __twarn(__VA_ARGS__, "")

// Hack to quiet the compiler. When VA_ARGS in twarn() has one element,
// e.g. twarn("OOM"), its replaced with __twarn("OOM", ""),
// thus VA_ARGS is expanded to at least one element in warn().
#define __twarn(fmt, ...) \
    warn("%s:%d in %s: " fmt "%s", __FILE__, __LINE__, __func__, __VA_ARGS__)

// Prints warning message on stderr in the format:
// <progname>: FILE:LINE in FUNC: <fmt>
#define twarnx(...) __twarnx(__VA_ARGS__, "")

// See __twarn macro.
#define __twarnx(fmt, ...) \
    warnx("%s:%d in %s: " fmt "%s", __FILE__, __LINE__, __func__, __VA_ARGS__)



int main()
{
        twarn("error1");
        twarnx("error2");
        return 0;
}

a.out: define.cpp:29 in main: error: Success
a.out: define.cpp:31 in main: twarnx

#include <iostream>

#define PA(a,b,...)     printf("%d %d %s\n", a, b, __VA_ARGS__)



int main()
{
        PA(1,4,"hello");
        return 0;
}

1 4 hello