2012-06-28 21:02
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const if语句是否与Go中的#ifdef宏具有相同的功能?

There's no text preprocessing in Go. Like Java and others like it, if I want to remove a block of code I can use a const value and surround the code with an if.

If I do this, does the compiler optimise the code from the AST and out of the generated code? Or is the condition executed each time?

EDIT: If I want to replicate #ifdef what's the best way to do it?

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Go中没有文本预处理功能。 像Java和其他类似的代码一样,如果要删除代码块,可以使用 const 值,并在代码中加上 if

如果执行此操作,编译器是否从AST优化代码并从生成的代码中优化代码? 还是每次都执行该条件?

编辑:如果我想复制 #ifdef ,什么是最好的方法? < / DIV>

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  • doubiao7410 2012-06-29 03:50

    If statements with constant conditions are not the same as #ifdef because the code inside is always compiled no matter what. However, the compilers do optimize it away when possible. Consider this program:

    package main
    import (
    func main() {
        if false {
            fmt.Println("Hello, world!")

    If we run go tool 6g -S test.go, here's the assembly output for the main function:

    --- prog list "main" ---
    0000 (test.go:7) TEXT    main+0(SB),$40-0
    0001 (test.go:11) RET     ,

    The dead code is gone so all it does is return.

    If you do need to actually conditionally compile parts of your code, it's best to do it through the build system.

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