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Re: Incompatible pointer types with GCC

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On 2016-12-16 18:07, Ben Bacarisse wrote:
> August Karlstrom <fusionfile@gmail.com> writes:
> The [] might confuse some people.  This is simply
>
>         void P(const Row *A)

I prefer to use brackets when a sequence is expected, it provides more 
semantic information.

>> test.c:3:6: note: expected ‘const int (*)[10]’ but argument is of type
>> ‘int (*)[10]’
>>  void P(const Row A[])
>>       ^
>
> I think gcc is right to complain.
>
> Whilst the types are not compatible, that's not really the problem here.
> For example, you can pass an int * to a function that takes const int *
> and those two types are not compatible.  Argument passing is done "as if
> by assignment", and in an assignment the pointed-to type on the left can
> have extra qualifiers.  But here, the const qualifies the element type,
> not the pointed-to type, which is an array type.  (C has not qualified
> array types at all).

That's counter-intuitive. I thought const applied to Row.

> The call is safe, of course, but C chose to use a simple rule rather
> than trying to identify only those calls (and assignments) that are not
> safe.  C++ has a more comprehensive rule.
>
> Cases like this (and passing to a const T ** parameter) are some of the
> rare times when you really need a cast.

OK, thanks for the clarification.


-- August

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Thread

Incompatible pointer types with GCC August Karlstrom <fusionfile@gmail.com> - 2016-12-16 11:41 +0100
  Re: Incompatible pointer types with GCC BartC <bc@freeuk.com> - 2016-12-16 11:06 +0000
  Re: Incompatible pointer types with GCC Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-12-16 17:07 +0000
    Re: Incompatible pointer types with GCC August Karlstrom <fusionfile@gmail.com> - 2016-12-16 23:02 +0100
      Re: Incompatible pointer types with GCC Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-12-17 00:48 +0000
      Re: Incompatible pointer types with GCC martin.uecker@med.uni-goettingen.de - 2016-12-18 08:06 -0800
        Re: Incompatible pointer types with GCC Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-12-18 20:11 +0000
          Re: Incompatible pointer types with GCC supercat@casperkitty.com - 2016-12-18 14:43 -0800
            Re: Incompatible pointer types with GCC Tim Rentsch <txr@alumni.caltech.edu> - 2016-12-29 13:33 -0800

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