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Re: C language declaration "bugs"

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On 11/10/2016 13:17, Thiago Adams wrote:

> But I think it s strange that I cannot use the same
> syntax for declarations in structs and functions.
>
> For instance:
>
> struct X
> {
>   int * a[]; //ERROR
>   int b[]; //ERROR
> };
>
> void f(int * a[]) { } //Ok
> void f2(int b[]) { } //Ok
>
> I was planning to use this syntax to document that for instance
>
> struct X{
> int b[];
> }
>
> b is a pointer to many ints.
>
> and
>
> int * b; would be used to document a pointer to just one int
>
> (also a tip for static analysis)

You've just discovered that C type declarations are a mess. As well as 
being context sensitive.

> when I do out of function scope
>
> //warning: array 'i' assumed to have one element
> int i[];
>
> So here is one more language suggestion:
>
> make empty array syntax the same of  "pointer" syntax.
>
>
> int i[]; the same of int *i;

That's going to be a problem because empty bounds are often used like this:

  int i[] = {10,20,30,40};

The bounds are now determined by the compiler (4 in this example). 
Requiring even that to be implemented by pointer will cause 
difficulties. And a mismatch between the above and:

  int j[4] = {10,20,30,40};

Here, i=0 would be legal, but not j=0;

It will also cause a mismatch (a serious one this time) when j is 
declared elsewhere as:

  extern int j[];

Here, you can't put in the bounds as you don't know what they are. 
(You'd have to put in a misleading dummy length.)

Also, in a function:

  void fn(int (*A)[]);

A has type 'pointer to unbounded array of int'. But you want [] to add 
an extra pointer to result in ... ?


-- 
Bartc



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Thread

C language declaration "bugs" Thiago Adams <thiago.adams@gmail.com> - 2016-10-11 05:17 -0700
  Re: C language declaration "bugs" Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-10-11 13:58 +0100
    Re: C language declaration "bugs" Thiago Adams <thiago.adams@gmail.com> - 2016-10-11 06:47 -0700
      Re: C language declaration "bugs" Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-10-11 15:03 +0100
        Re: C language declaration "bugs" Thiago Adams <thiago.adams@gmail.com> - 2016-10-11 07:41 -0700
          Re: C language declaration "bugs" BartC <bc@freeuk.com> - 2016-10-11 16:31 +0100
        Re: C language declaration "bugs" Keith Thompson <kst-u@mib.org> - 2016-10-11 10:01 -0700
          Re: C language declaration "bugs" Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-10-11 19:10 +0100
  Re: C language declaration "bugs" BartC <bc@freeuk.com> - 2016-10-11 14:14 +0100

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