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Groups > comp.lang.c > #105761
| From | Noob <root@127.0.0.1> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: Return statement: anything goes? |
| Date | 2017-03-10 22:06 +0100 |
| Organization | A noiseless patient Spider |
| Message-ID | <o9v4bu$u23$1@dont-email.me> (permalink) |
| References | <o9utno$5tn$1@dont-email.me> |
On 10/03/2017 20:13, BartC wrote:
> This is something that came up last week, and was another example of C
> compilers all reacting differently to the same errors.
>
> In this case, whether or not a return statement is present, and whether
> it returns the correct type of expression:
>
> int V;
>
> void A1(int x) { }
> void A2(int x) { return;}
> void A3(int x) { return 123;}
>
> int B1(int x) { }
> int B2(int x) { return;}
> int B3(int x) { return 123;}
> int B4(int x) { return &V;}
> int B5(int x) { if (1) return x;}
>
> void* C1(int x) { }
> void* C2(int x) { return;}
> void* C3(int x) { return 123;}
> void* C4(int x) { return &V;}
>
> int main(void) { } // M1
> int main(void) { return;} // M2
> int main(void) { return 123;} // M3
> int main(void) { return &V;} // M4
>
> (The main() variations were tested one at a time.)
>
> A selection of Windows C compilers gave these errors and warnings with
> default options (E = error, W = warning, dash = no error):
>
> A1 A2 A3 B1 B2 B3 B4 B5 C1 C2 C3 C4 M1 M2 M3 M4
>
> Pelles C - - W W E - E - - E E - - E - E
> lccwin - - W W W - E W W W E - - W - W
> DMC - - - - E - E - - - E - - - - E
> gcc/tdm - - W - W - W - - W W - - W - W
> Tiny C - - - - - - W - - - W - - - - W
> MSVC'08 - - W W W - W - W W W - - - - -
>
> (bartc - - E E E - E E E E E - * E - E)
>
> The last row shows what I consider to be errors, where I wouldn't be
> happy with a wrong or missing return statement making it into code that
> is to be executed.
>
> It does rather seem that compiling C code is something of a lucky dip!
> Surely source code is either correct or it isn't? Or is part of the
> problem an attempt to keep compatibility with lax code and lax compilers
> of the past?
What version of gcc are you testing with?
You might want to try running your test with
gcc -O2 -std=c99 -Wall -Werror
You'd get errors for A3, B1, B2, B4, C1, C2, C3.
(I didn't test the M* cases.)
Why do you expect an error for B5?
> [* I assume special rules apply to main(), in that a missing return
> statement, or return expression, is quietly replaced by 'return 0']
No need to assume. You can look it up in the standard.
http://port70.net/~nsz/c/c11/
http://port70.net/~nsz/c/c99/
Regards.
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Return statement: anything goes? BartC <bc@freeuk.com> - 2017-03-10 19:13 +0000
Re: Return statement: anything goes? John Bode <jfbode1029@gmail.com> - 2017-03-10 11:59 -0800
Re: Return statement: anything goes? Keith Thompson <kst-u@mib.org> - 2017-03-10 12:34 -0800
Re: Return statement: anything goes? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-03-10 20:17 +0000
Re: Return statement: anything goes? bart4858@gmail.com - 2017-03-10 13:17 -0800
Re: Return statement: anything goes? Ian Collins <ian-news@hotmail.com> - 2017-03-11 10:30 +1300
Re: Return statement: anything goes? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-03-11 01:25 +0000
Re: Return statement: anything goes? BartC <bc@freeuk.com> - 2017-03-11 12:11 +0000
Re: Return statement: anything goes? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-03-11 14:57 +0000
Re: Return statement: anything goes? BartC <bc@freeuk.com> - 2017-03-11 16:31 +0000
Re: Return statement: anything goes? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-03-11 17:47 +0000
Re: Return statement: anything goes? BartC <bc@freeuk.com> - 2017-03-11 17:57 +0000
Re: Return statement: anything goes? jameskuyper@verizon.net - 2017-03-11 10:59 -0800
Re: Return statement: anything goes? BartC <bc@freeuk.com> - 2017-03-11 19:34 +0000
Re: Return statement: anything goes? jameskuyper@verizon.net - 2017-03-11 11:59 -0800
Re: Return statement: anything goes? supercat@casperkitty.com - 2017-03-11 12:26 -0800
Re: Return statement: anything goes? supercat@casperkitty.com - 2017-03-11 12:22 -0800
Re: Return statement: anything goes? jameskuyper@verizon.net - 2017-03-11 12:42 -0800
Re: Return statement: anything goes? supercat@casperkitty.com - 2017-03-11 13:01 -0800
Re: Return statement: anything goes? Gordon Burditt <gordon@hammy.burditt.org> - 2017-03-13 16:25 -0500
Re: Return statement: anything goes? Gareth Owen <gwowen@gmail.com> - 2017-03-11 16:43 +0000
Re: Return statement: anything goes? BartC <bc@freeuk.com> - 2017-03-11 18:13 +0000
Re: Return statement: anything goes? BartC <bc@freeuk.com> - 2017-03-11 18:27 +0000
Re: Return statement: anything goes? gordonb.rlpr3@burditt.org (Gordon Burditt) - 2017-03-13 16:18 -0500
Re: Return statement: anything goes? supercat@casperkitty.com - 2017-03-11 12:44 -0800
Re: Return statement: anything goes? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2017-03-11 07:43 -0800
Re: Return statement: anything goes? BartC <bc@freeuk.com> - 2017-03-11 18:34 +0000
Re: Return statement: anything goes? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2017-03-11 10:43 -0800
Re: Return statement: anything goes? Keith Thompson <kst-u@mib.org> - 2017-03-10 12:27 -0800
Re: Return statement: anything goes? Noob <root@127.0.0.1> - 2017-03-10 22:06 +0100
Re: Return statement: anything goes? bart4858@gmail.com - 2017-03-10 13:26 -0800
Re: Return statement: anything goes? antispam@math.uni.wroc.pl - 2017-03-12 05:29 +0000
Re: Return statement: anything goes? BartC <bc@freeuk.com> - 2017-03-12 10:52 +0000
Re: Return statement: anything goes? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-03-12 12:19 +0000
Re: Return statement: anything goes? BartC <bc@freeuk.com> - 2017-03-12 12:51 +0000
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