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From: comeau@ditka.Chicago.COM (Greg Comeau)
Newsgroups: comp.std.c++
Subject: Re: Proposed: "closures"
Keywords: proposal, closures, function pointers
Message-ID: <38855@ditka.Chicago.COM>
Date: 14 May 91 14:19:41 GMT
Article-I.D.: ditka.38855
References: <1991Apr30.201532.13706@kestrel.edu> <1991May10.003304.12390@mathcs.sjsu.edu> <1991May12.194247.21483@news.cs.brandeis.edu>
Sender: comeau@ditka.Chicago.COM (Greg Comeau)
Reply-To: comeau@csanta.attmail.com (Greg Comeau)
Distribution: comp.std.c++
Organization: Comeau Computing
Lines: 40

In article <1991May12.194247.21483@news.cs.brandeis.edu> bs@chaos.cs.brandeis.edu (Benjamin Schreiber) writes:
>In article <1991May10.003304.12390@mathcs.sjsu.edu> horstman@mathcs.sjsu.edu (Cay Horstmann) writes:
>>Just out of curiosity: Suppose I have a variable f that holds a pointer
>>to a "C" style void->void function and I want to make f local to its source
>>file, do I say    static extern "C" void (*f)();

No, that is a declaration with 2 storage class specifiers
that differ in their linkage demands.

>From reading the grammar, I get the feeling that the correct way to do this
>is: extern "C" { static void (*f)(); };

It is.

>Since any declarations/definitions are gramaticly allowed inside an extern
>construct.  The following may also be valid: extern "C" static void (*f)();

It is not.  That still contained 2 storage class specifiers with different
linkage.

Getting back to the original data type though.  This:

    extern "C" { static void (*f)(); };

is not "a variable f that holds a pointer to a "C" style void->void function".
Instead it is f that is being extern C'd.  The correct decl for the original
problem would be:

    extern "C" typedef void (*ptCf)();
    [static] ptCf f;

This typedef ugliness must be used.  I honestly don't know how many
compilers accept this though.

- Greg
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