C++预处理宏实战

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一 标准宏的例子

1 代码

#include <iostream>
using namespace std;
// 标准宏名称
#include <iostream>
using namespace std;

int main()
{
    cout << "This is the line number "
         << __LINE__;
    cout << " of file " << __FILE__
         << ".\n";
    cout << "Its compilation began "
         << __DATE__;
    cout << " at " << __TIME__ << ".\n";
    cout << "The compiler gives a "
         << "__cplusplus value of "
         << __cplusplus;
    cout << endl;
    return 0;
}

2 运行

[root@localhost test]# g++ test.cpp -g -o test
[root@localhost test]# ./test
This is the line number 10 of file test.cpp.
Its compilation began Mar 18 2019 at 21:40:16.
The compiler gives a __cplusplus value of 199711

二 使用宏__func__得到函数名

1 代码

#include<stdio.h>
const char *test()
{
  return __func__;
}
int main ()
{
  printf("%s,%s",__func__,test());
  return 0;
}

2 运行

[root@localhost test]# g++ test1.cpp -g -o test1
[root@localhost test]# ./test1
main,test

三 变长参数的宏

1 代码

#include<stdio.h>
#define DBGDUMP(...) \
{ \
  printf("%s\n%s,%d\n",__FILE__,__func__,__LINE__); \
  printf(__VA_ARGS__); \
}
int main ()
{
  int ret = 5;
  DBGDUMP("ret=%d\n",ret);
  return 0;
}

2 运行

[root@localhost test]# g++ test1.cpp -g -o test1
[root@localhost test]# ./test1
test1.cpp
main,10
ret=5