douliang2935
2018-12-04 08:10
浏览 121

如何使用CGO将字符串从函数返回到Ruby

I have a function in Go:

func login(user *C.char) *C.char {
    cstr := C.CString("Hello World")
    defer C.free(unsafe.Pointer(cstr))
    return cstr 
}

My ruby code as below

module GoLib
  extend FFI::Library
  ffi_lib './golib.so'

  attach_function :login, [:string], :string
end

GoLib.login("User1") #=> "p\x9A\xA0\xDB\x16V"

it does not return as ruby string. How to I fix this?

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1条回答 默认 最新

  • donglian4879 2018-12-04 15:55
    已采纳

    As stated in the comments, cstr gets free'd after control has been passed to Ruby. Here is a workaround where you explicitly manage the pointer in Ruby.

    package main
    
    // #include <stdlib.h>
    import "C"
    import "unsafe"
    
    //export login
    func login(user *C.char) *C.char {
        return C.CString("Hello from Go")
    }
    
    //export logout
    func logout(c *C.char) {
        C.free(unsafe.Pointer(c))
    }
    
    func main() {}
    

    In Ruby:

    require 'ffi'
    
    module GoLib
      extend FFI::Library
      ffi_lib './so.so'
    
      attach_function :login, [:string], :strptr
      attach_function :logout, [:pointer], :void
    end
    
    s, p = GoLib.login("User1")
    puts s
    p = FFI::AutoPointer.new(p, GoLib.method(:logout))
    

    Note the use of strptr as demonstrated here

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