C-style conditional compilation in golang

Question

Does golang support

#define DEBUG   #ifdef DEBUG    fmt.Println("Debug message...");  #endif  

So I can build a debug version with zero runtime overhead?

Answer 1

Go does not have a preprocessor or a macro system. What you could do is pass in tags to go build through the -tags flag and use build constraints. To do this you would need two versions of the same source and only one would get build depending if the tag is present or not.

Look at build constraints in https://golang.org/pkg/go/build/

main_debug.go

// +build debug  package main  import (     "fmt" )  func main() {     fmt.Println("Debug build") } 

main_release.go

// +build !debug  package main  import (     "fmt" )  func main() {     fmt.Println("Release build") } 

Here go build would compile with main_release.go and go build -tags debug would compile with main_debug.go

Answer 2

if you work on linux or Mac , you can try the "m4" command.This command is a macro processor which just fits this issue.

Writing a Makefile to run the m4 command before "go build" can do the same as using "go build -tags ..." and support more customization and of course, save your work.

for example:

write these within your go file(such as main.go):

define(DEBUG) ifdef(`DEBUG',     fmt.Println("Debug message...");  ) 

write these within your Makefile file:

all:*.go     mv main.go main.go.bak     m4 main.go.bak > main.go     go build     mv main.go.bak main.go 

then run "make".

Disadvantage:

1. You can't write a go function named "define" or "ifndef" etc which will be translated into Macro by m4.
2. If you have a lot of files you may want to improve your Makefile.
3. You may want to study m4 which is a little difficult and complicated.