typedef struct and enum, why? [duplicate]

This question already has answers here: Closed 11 years ago.

Possible Duplicates:

Purpose of struct, typedef struct, in C++

typedef struct vs struct definitions

In code that I am mai开发者_JAVA技巧ntaining I often see the following:

typedef enum { blah, blah } Foo;
typedef struct { blah blah } Bar;

Instead of:

enum Foo { blah, blah };
struct Bar { blah blah };

I always use the latter, and this is the first time I am seeing the former. So the question is why would one use one style over the other. Any benefits? Also are they functionally identical? I believe they are but am not 100% sure.

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In C++ this doesn't matter.

In C, structs, enums, and unions were in a different "namespace", meaning that their names could conflict with variable names. If you say

struct S { };

So you could say something like

struct S S;

and that would mean that struct S is the data type, and S is the variable name. You couldn't say

S myStruct;

in C if S was a struct (and not a type name), so people just used typedef to avoid saying struct all the time.

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They are for C compatability. A normal

  struct Bar { blah, blah };

doesn't work the same with C;