postmaster.c 中的 ListenAddresses

在 postmaster.c 中看到这种代码，从Java程序员的角度，看起来是很不爽的:

char *ListenAddresses;
...if (ListenAddresses){            char       *rawstring;            List       *elemlist;            ListCell   *l;                
...

到底何时 ListenAddress 的逻辑值为真呢？试作如下代码进行验证：

char *ListenAddresses;int
main(int argc, char **argv)
{if (ListenAddresses){fprintf(stderr, "ListenAddresses is ok.\n");}else{fprintf(stderr, "ListenAddresses is NG.\n");}return 0;
}

编译后运行结果：ListenAddresses is NG.

再改改，运行看看：

char *ListenAddresses;int
main(int argc, char **argv)
{ListenAddress="192.168.2.5";if (ListenAddress){fprintf(stderr, "ListenAddresses is ok.\n");fprintf(stderr, "ListenAddresses is %s.\n",ListenAddress);}else{fprintf(stderr, "ListenAddresses is NG.\n");}return 0;
}

运行结果：

ListenAdresses is ok.
ListenAddresses is 192.168.2.5.