Put together function name from type in macro

This is a discussion on Put together function name from type in macro within the C Programming forums, part of the General Programming Boards category; Hi! I'm doing some experimentation with C and trying some stuff out. Right now I am playing around with macros ...

  1. #1
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    Put together function name from type in macro

    Hi!

    I'm doing some experimentation with C and trying some stuff out.
    Right now I am playing around with macros and I found the GCC typeof keyword which I found intriging.

    Anyway so I am trying to make a "initializer" macro which will more or less take any type of structure and call it's "construct function"

    More or less something like this:
    Code:
    SomeType foo;
    construct( foo ); // Becomes -> SomeType_Construct( &foo );
    Though I am having problem with pasting together the type and the _Construct and is wondering if anyone else know what to do or got a better idea?

    Doing this doesn't work as it tries to construct this string: typeof( object )_Construct( &object )
    Code:
    #define construct( object ) typeof( object )##_Construct( &object )
    If you got a better way you know to solve the same problem then of course I am interested in that as well.

  2. #2
    Master Apprentice phantomotap's Avatar
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    O_o

    That's not going to work.

    The `typeof' thing is not a macro to be expanded; it is an operator (keyword) like `sizeof'.

    The `typeof', like `sizeof', resolves during compilation proper and not the processing phase.

    Soma

  3. #3
    Algorithm Dissector iMalc's Avatar
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    Rather than trying to fake constructors in C, I suggest you learn a little C++.
    My homepage
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    Probably best. I had a bit of a think about this, as the post by the OP would have been quite a nice and simple trick if it worked. I couldn't think of anything much though - nothing that hasn't been covered in various places.

    Quote Originally Posted by Groogy
    Anyway so I am trying to make a "initializer" macro which will more or less take any type of structure and call it's "construct function"
    Yeah. C++. Definitely. Constructors. Automatically called when you create the struct. Failing that, you can do it your way with overloaded functions, define construct() functions with different types, but I wouldn't bother.

  5. #5
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    The last C standard defines a new construct to do exactly that, without compiler extension like typeof(), but it's only supported by clang and gcc (?) so far.
    Code:
    #define construct(x) _Generic((x),\
        char: construct_char,\
        int: construct_int,\
        struct foo: construct_st_foo,\
        ...)(x)
    Google "c11 _Generic" for examples.

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