dongse5408
2014-04-15 11:11
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与CGO正确使用空结构

Working with gssapi.h

struct gss_name_struct;
typedef struct gss_name_struct * gss_name_t;

I am trying to figure out how to properly initialize a variable containing this by

var output_name C.gss_name_t = &C.struct_gss_name_struct{}

But the functions like gss_import_name act like if I was passing null pointer to them. What is the correct way to properly initialize and use these empty structs with CGO?

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1条回答 默认 最新

  • dpevsxjn809817 2014-04-15 14:00
    已采纳

    Go's strict typing makes typedefs a pain to work with. The best way to make your Go look clear is to write a small wrapper function in C to build the struct exactly how you want it. In this case though, go is using a zero-length byte array for an empty C struct, which you can verify below. You can declare it directly in go, and convert it when necessary.

    Since C isn't strict with types, using type inference is often the easiest way to assign the type that Go expects. There's also a trick using the cgo tool to show the type declarations you need. Using go tool cgo -godefs filename.go will output the cgo definitions for your types. As you see though, the go equivalent types could get a little messy.

    // statement in the original .go file
    //var output_name C.gss_name_t = &C.struct_gss_name_struct{}
    
    // output from cgo -godefs
    // var output_name *[0]byte = &[0]byte{}
    
    // or more succinctly
    output_name := &[0]byte{}
    
    // output_name can be converted directly to a C.gss_name_t
    fmt.Printf("%+v
    ", output_name)
    fmt.Printf("%+v
    ", C.gss_name_t(output_name))
    
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