33用d编程编译指示

import std.string;

void func(A, B)(A a, B b) {
    pragma(msg, format("用'%s'和'%s'调用",A.stringof, B.stringof));
    // ...
}

void main() {
    func(42, 1.5);
    func("你好", 'a');
}

编译时生成消息.运行时没有.
pragma(lib,"curl");指示与哪个库连接
pragma(inline)指定是否内联.

import std.stdio;
import std.datetime;//StopWatch
ubyte compute(ubyte i) {
    return cast(ubyte)(i * 42);
}

void main() {
    size_t counter = 0;

    StopWatch sw;
    sw.start();

    foreach (i; 0 .. 10000_0000) {//1亿次
        const number = cast(ubyte)i;
        if (compute(number) == number) {
            ++counter;
        }
        //const r= cast(ubyte)(number * 42);
        //if(r == number) {//等价内联
    }

    sw.stop();

    writefln("%s毫秒", sw.peek.msecs);
}

命令行$ dmd deneme.d -w -inline
调用函数内联.缺点是,有时代码体太多太膨胀.
pragma(inline, false):,即使编译器有内联选项也不内联.
pragma(inline, true),一定内联,编译器无法内联时会报错.
pragma(inline),由编译器选项-inline决定.

pragma(inline, false) {
    // 不应内联
    // ...
}

int foo() {
    pragma(inline, true);  //应内联
    // ...
}

pragma(inline, true):
// 应该内联
// ...

pragma(inline):
// 由编译器`-inline`决定
// ...

pragma(startaddress)指示程序起始地址.
pragma(mangle)指示混杂符号

//这样用
pragma(mangle, "body")
extern(C) string c_body(string);
void main() {
    auto s = c_body("hello");//真实名字为`body`
}

当然进行c++等的链接时也很有用.