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Re: Call to a function

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Phil Carmody <pc+usenet@asdf.org> writes:

> Tim Rentsch <tr.17687@z991.linuxsc.com> writes:
>
>> Keith Thompson <Keith.S.Thompson+u@gmail.com> writes:
>>
>>> Tim Rentsch <tr.17687@z991.linuxsc.com> writes:
>>>
>>>> [...]  Does the C standard allow an
>>>> implementation to reject any program that is not strictly
>>>> conforming?

[...]

>> Let's consider a concrete example.  This program
>>
>>     #include <stdio.h>
>>     #include <stdint.h>
>>
>>     extern char large[2305843009213693952];
>>
>>     int
>>     main( void ){
>>         printf( "Hello, world\n" );
>>         printf( "\n" );
>>         printf( "SIZE_MAX is %21zu\n", SIZE_MAX );
>>         printf( "  large has %21zu  bytes\n", sizeof large );
>>         printf( "\n" );
>>         printf( "(... that's all, folks! ...)\n" );
>>         return  0;
>>     }
>>
>> is, if I am not mistaken, free of any undefined behavior.  It can
>> be compiled and run, for example by gcc on a 64-bit linux system.
>> Yet if we ask clang to compile it on the same system, clang gives
>> an error complaining that the array is too large.  Note that the
>> same program, except with a one-smaller value of the array
>> dimension, can be compiled by clang without complaint, and run
>> successfully.  Clearly the clang implementors feel that the C
>> standard allows them not to accept this program, and the only
>> reason I can see for that is that the program is not strictly
>> conforming, because it exceeds a minimum implementation limit.
>>
>> Long story short:  in how it treats this program, clang agrees
>> with my reading of the C standard.  Incidentally, gcc has the
>> same behavior as clang, only with a larger value of the array
>> dimension.
>
> Is your conclusion the same if the variable is scrapped and the
> printf is given the type instead?

The short answer is yes.

The lower bound for SIZE_MAX is 65535.  As I read the C standard,
any object or any type whose 'sizeof' is bigger than 65535 means
the program exceeds a minimum implementation limit, and is
therefore not strictly conforming.  Because it is not strictly
conforming, implementations are free not to accept it.

> clang retains its stance on the concept:
>
> """
> phil@dovespaz:~$ clang -Wall -o crap crap.c
> crap.c:11:59: error: array is too large (2305843009213693952 elements)
>    printf( "  large has %21zu  bytes\n", sizeof(char[2305843009213693952]));
>                                                      ^~~~~~~~~~~~~~~~~~~
> 1 error generated.
> """
>
> Is there an "array", /per se/?  I only see a type.

An array type, but no array object.  I think most people would say
there isn't an array, but just a type.

> clang does seem to agree with me that it's a type it's looking at,
> [...]

Right, the operand of that sizeof is syntactically a type, not an
expression (or more specifically, what the C standard calls a "type
name").

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Re: Call to a function Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-11-10 03:37 -0800
  Re: Call to a function Kaz Kylheku <864-117-4973@kylheku.com> - 2023-11-10 22:04 +0000
    Re: Call to a function Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-11-13 08:14 -0800
  Re: Call to a function Phil Carmody <pc+usenet@asdf.org> - 2023-11-13 21:35 +0200
    Re: Call to a function Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-11-13 12:48 -0800
    Re: Call to a function Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-11-13 19:17 -0800
      Re: Call to a function Phil Carmody <pc+usenet@asdf.org> - 2023-11-16 13:47 +0200
        Re: Call to a function Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-11-16 06:39 -0800
          Re: Call to a function Phil Carmody <pc+usenet@asdf.org> - 2023-11-21 01:29 +0200
            Re: Call to a function James Kuyper <jameskuyper@alumni.caltech.edu> - 2023-11-21 23:21 -0500
            Re: Call to a function Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-12-24 11:12 -0800

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