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Groups > comp.lang.c > #143035
| From | Keith Thompson <kst-u@mib.org> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: Scopes of identifiers |
| Date | 2019-04-11 14:00 -0700 |
| Organization | None to speak of |
| Message-ID | <ln7ec02r73.fsf@kst-u.example.com> (permalink) |
| References | <098da5fe-31d3-47b7-b695-d4faea10b366@googlegroups.com> <e9d0004b-6a21-43ef-98f6-16ed2152d985@googlegroups.com> <lnk1g12nx8.fsf@kst-u.example.com> <q8o2mg$21k$1@dont-email.me> |
Andrey Tarasevich <andreytarasevich@hotmail.com> writes:
> On 4/10/2019 8:58 PM, Keith Thompson wrote:
>> For example, an old "hello, world" program might look something like
>> this:
>>
>> main() {
>> int printf();
>> printf("hello, world\n");
>> }
>>
>> but in modern C you'd just #include <stdio.h>. (Actually in ancient C
>> you probably wouldn't have bothered to declare printf, since it returns
>> an int and the call would be resolved correctly.)
>
> This is not entirely accurate. A variadic function (like `printf`) has
> to be declared *with prototype*. Calling a variadic function without a
> declaration or with a non-prototype declaration results in undefined
> behavior. This requirement is present in the language since C89.
>
> The correct version would be
>
> int main()
> {
> int printf(const char *, ...);
> printf("hello, world\n");
> }
Of course I'm aware of that (and I should have mentioned it). It was
meant to be an example of a pre-ANSI C program, written when the
language didn't have prototypes or explicitly variadic functions.
In modern C, you could write:
int main(void) {
int printf(const char *restrict format, ...);
printf("hello, world\n");
}
but it's a lot easier just to write:
#include <stdio.h>
int main(void) {
printf("hello, world\n");
}
(and not have to worry about whether "restrict" is supported and/or
needed). But in pre-ANSI C, this:
printf();
or this:
int printf();
would have been the only available way to declare printf.
As someone pointed out, a floating-point function might have made for a
better example:
/* This is pre-ANSI */
main() {
double sqrt();
printf("%f\n", sqrt(2.0));
}
--
Keith Thompson (The_Other_Keith) kst-u@mib.org <http://www.ghoti.net/~kst>
Will write code for food.
void Void(void) { Void(); } /* The recursive call of the void */
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Scopes of identifiers Thiago Adams <thiago.adams@gmail.com> - 2019-04-10 16:15 -0700
Re: Scopes of identifiers Bart <bc@freeuk.com> - 2019-04-11 00:33 +0100
Re: Scopes of identifiers Thiago Adams <thiago.adams@gmail.com> - 2019-04-10 16:45 -0700
Re: Scopes of identifiers Thiago Adams <thiago.adams@gmail.com> - 2019-04-10 18:31 -0700
Re: Scopes of identifiers Thiago Adams <thiago.adams@gmail.com> - 2019-04-10 16:34 -0700
Re: Scopes of identifiers Robert Wessel <robertwessel2@yahoo.com> - 2019-04-10 20:50 -0500
Re: Scopes of identifiers James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-04-10 20:02 -0700
Re: Scopes of identifiers Keith Thompson <kst-u@mib.org> - 2019-04-10 20:58 -0700
Re: Scopes of identifiers luser droog <luser.droog@gmail.com> - 2019-04-10 21:48 -0700
Re: Scopes of identifiers Andrey Tarasevich <andreytarasevich@hotmail.com> - 2019-04-11 11:57 -0700
Re: Scopes of identifiers scott@slp53.sl.home (Scott Lurndal) - 2019-04-11 19:12 +0000
Re: Scopes of identifiers Thiago Adams <thiago.adams@gmail.com> - 2019-04-11 12:35 -0700
Re: Scopes of identifiers Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-04-12 01:11 +0100
Re: Scopes of identifiers Thiago Adams <thiago.adams@gmail.com> - 2019-04-12 05:29 -0700
Re: Scopes of identifiers Thiago Adams <thiago.adams@gmail.com> - 2019-04-12 05:39 -0700
Re: Scopes of identifiers Keith Thompson <kst-u@mib.org> - 2019-04-11 14:00 -0700
Re: Scopes of identifiers Nick Bowler <nbowler@draconx.ca> - 2019-04-15 19:48 +0000
Re: Scopes of identifiers Bart <bc@freeuk.com> - 2019-04-11 10:36 +0100
Re: Scopes of identifiers Bart <bc@freeuk.com> - 2019-04-11 14:25 +0100
Re: Scopes of identifiers Keith Thompson <kst-u@mib.org> - 2019-04-11 10:20 -0700
Re: Scopes of identifiers Thiago Adams <thiago.adams@gmail.com> - 2019-04-11 05:00 -0700
Re: Scopes of identifiers Thiago Adams <thiago.adams@gmail.com> - 2019-04-11 06:42 -0700
Re: Scopes of identifiers James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-04-11 08:11 -0700
Re: Scopes of identifiers BGB <cr88192@gmail.com> - 2019-04-10 22:35 -0500
Re: Scopes of identifiers Keith Thompson <kst-u@mib.org> - 2019-04-10 22:04 -0700
Re: Scopes of identifiers BGB <cr88192@gmail.com> - 2019-04-11 05:46 -0500
Re: Scopes of identifiers John Bode <jfbode1029@gmail.com> - 2019-04-11 12:04 -0700
Re: Scopes of identifiers James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-04-11 13:18 -0700
Re: Scopes of identifiers Keith Thompson <kst-u@mib.org> - 2019-04-11 14:31 -0700
Re: Scopes of identifiers Andrey Tarasevich <andreytarasevich@hotmail.com> - 2019-04-11 12:28 -0700
Re: Scopes of identifiers Thiago Adams <thiago.adams@gmail.com> - 2019-04-11 12:50 -0700
Re: Scopes of identifiers James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-04-11 14:20 -0700
Re: Scopes of identifiers Thiago Adams <thiago.adams@gmail.com> - 2019-04-11 14:43 -0700
Re: Scopes of identifiers Andrey Tarasevich <andreytarasevich@hotmail.com> - 2019-04-11 15:04 -0700
Re: Scopes of identifiers Keith Thompson <kst-u@mib.org> - 2019-04-11 17:08 -0700
Re: Scopes of identifiers Andrey Tarasevich <andreytarasevich@hotmail.com> - 2019-04-11 18:45 -0700
Re: Scopes of identifiers James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-04-11 23:16 -0400
Re: Scopes of identifiers Keith Thompson <kst-u@mib.org> - 2019-04-11 20:19 -0700
Re: Scopes of identifiers Tim Rentsch <tr.17687@z991.linuxsc.com> - 2019-04-12 14:39 -0700
Re: Scopes of identifiers Ike Naar <ike@sdf.lonestar.org> - 2019-04-13 20:02 +0000
Re: Scopes of identifiers James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-04-11 23:26 -0400
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