Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]
Groups > comp.compilers > #1748
| From | Kaz Kylheku <221-501-9011@kylheku.com> |
|---|---|
| Newsgroups | comp.compilers |
| Subject | Re: Alternative C compilers on x86_64 Linux? |
| Date | 2016-09-06 02:15 +0000 |
| Organization | Aioe.org NNTP Server |
| Message-ID | <16-09-009@comp.compilers> (permalink) |
| References | <16-09-001@comp.compilers> <16-09-005@comp.compilers> |
On 2016-09-05, BartC <bc@freeuk.com> wrote:
> On 02/09/2016 04:01, Aharon Robbins wrote:
>
>> TinyCC is blindingly fast, and can compile gawk, but is broken in that
>> it won't diagnose duplicate case statements inside switch. The developers
>> don't consider this a problem. So I refuse to use it.
>>
>> In short, I'm looking for a faster compiler that actually works.
>
> I'm quite impressed with Tiny CC. I'd considered it a toy compiler that
> could only compile a small subset of the language until I actually tried it.
>
> And yes, on my Win64 version, it does seem to ignore duplicate 'case'
> labels.
>
> But TCC does have problem with compiling switch statements; although the
> code it generates isn't that great anyway, that for switches is slower.
>
> I suspect it just compiles switch as an if-else chain. Which might
> explain why duplicate case labels are ignored if that conversion is done
> at at early stage.
>
> (Because a duplicate condition in an if-else chain is fine. For a
> jump-table of course, a duplicate label is ambiguous so can't be allowed.)
A duplicate condition in an if-else chain is unreachable code, which is
probably a bug.
if (foo) {
...
} else if (foo) {
/* unreachable */
} else if (bar) {
...
}
Duplicate cases are a constraint violation in ISO C, requiring a
diagnostic.
A duplicate label can also be just as "fine". Look, you can build a jump
table, and then just fill it without caring about duplicates:
case 42:
...
case 42:
No problem: just write to jumptable[42] twice, letting it the most
recently established address overrule the previous one.
Duplicate case label code can still be reachable, making the bugs
potentially more interesting:
case 42: // suppose this is used
...
break;
case 19:
...
/* fallthrough */
case 42: // this isn't used, but fallthrough makes it reachable
--
TXR Programming Lanuage: http://nongnu.org/txr
Music DIY Mailing List: http://www.kylheku.com/diy
ADA MP-1 Mailing List: http://www.kylheku.com/mp1
Back to comp.compilers | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread
Alternative C compilers on x86_64 Linux? arnold@skeeve.com (Aharon Robbins) - 2016-09-02 03:01 +0000
Re: Alternative C compilers on x86_64 Linux? jacobnavia <jacob@jacob.remcomp.fr> - 2016-09-05 00:20 +0200
Re: Alternative C compilers on x86_64 Linux? alexfrunews@gmail.com - 2016-09-05 17:26 -0700
Re: diagnosing C errors, was Alternative C compilers on x86_64 Linux? BartC <bc@freeuk.com> - 2016-09-09 12:31 +0100
Re: diagnosing C errors, was Alternative C compilers on x86_64 Linux? Kaz Kylheku <221-501-9011@kylheku.com> - 2016-09-09 16:06 +0000
Re: diagnosing C errors, was Alternative C compilers on x86_64 Linux? Hans-Peter Diettrich <DrDiettrich1@netscape.net> - 2016-09-10 00:38 +0200
Re: Alternative C compilers on x86_64 Linux? Nemo <nemo@invalid.invalid> - 2016-09-04 18:32 -0400
Re: Alternative C compilers on x86_64 Linux? Kaz Kylheku <221-501-9011@kylheku.com> - 2016-09-04 23:48 +0000
Re: Alternative C compilers on x86_64 Linux? BartC <bc@freeuk.com> - 2016-09-05 13:19 +0100
Re: Alternative C compilers on x86_64 Linux? Kaz Kylheku <221-501-9011@kylheku.com> - 2016-09-06 02:15 +0000
Re: Alternative C compilers on x86_64 Linux? BartC <bc@freeuk.com> - 2016-09-06 21:35 +0100
Re: dead code or otherwise, was Alternative C compilers on x86_64 Linux? George Neuner <gneuner2@comcast.net> - 2016-09-08 11:58 -0400
Re: dead code or otherwise, was Alternative C compilers on x86_64 Linux? Kaz Kylheku <221-501-9011@kylheku.com> - 2016-09-08 22:54 +0000
Re: dead code or otherwise, was Alternative C compilers on x86_64 Linux? George Neuner <gneuner2@comcast.net> - 2016-09-09 00:51 -0400
Re: dead code or otherwise, was Alternative C compilers on x86_64 Linux? Kaz Kylheku <221-501-9011@kylheku.com> - 2016-09-09 06:05 +0000
Re: dead code or otherwise, was Alternative C compilers on x86_64 Linux? George Neuner <gneuner2@comcast.net> - 2016-09-09 14:02 -0400
Re: dead code or otherwise, was Alternative C compilers on x86_64 Linux? Kaz Kylheku <221-501-9011@kylheku.com> - 2016-09-09 19:57 +0000
Re: duplicate cases, was Alternative C compilers on x86_64 Linux? Andy Walker <anw@cuboid.co.uk> - 2016-09-07 17:01 +0100
Re: Alternative C compilers on x86_64 Linux? Florian Weimer <fw@deneb.enyo.de> - 2016-09-05 20:06 +0200
Re: Alternative C compilers on x86_64 Linux? alexfrunews@gmail.com - 2016-09-05 17:22 -0700
Re: Alternative C compilers on x86_64 Linux? Kaz Kylheku <221-501-9011@kylheku.com> - 2016-09-06 02:18 +0000
Re: Alternative C compilers on x86_64 Linux? rockbrentwood@gmail.com - 2016-09-07 17:00 -0700
Re: Alternative C compilers on x86_64 Linux? arnold@skeeve.com (Aharon Robbins) - 2016-09-12 18:42 +0000
Re: Alternative C compilers on x86_64 Linux? BartC <bc@freeuk.com> - 2016-09-12 22:37 +0100
Re: Alternative C compilers on x86_64 Linux? arnold@skeeve.com (Aharon Robbins) - 2016-09-13 17:35 +0000
Re: Alternative C compilers on x86_64 Linux? arnold@skeeve.com (Aharon Robbins) - 2016-09-14 18:14 +0000
Re: Alternative C compilers on x86_64 Linux? rugxulo@gmail.com - 2016-09-26 15:29 -0700
Re: Alternative C compilers on x86_64 Linux? arnold@skeeve.com (Aharon Robbins) - 2016-09-27 05:40 +0000
Re: Alternative C compilers on x86_64 Linux? rugxulo@gmail.com - 2016-09-27 16:36 -0700
Re: Alternative C compilers on x86_64 Linux? BartC <bc@freeuk.com> - 2016-09-28 18:16 +0100
Re: Alternative C compilers on x86_64 Linux? BartC <bc@freeuk.com> - 2016-09-29 14:03 +0100
Re: Alternative C compilers on x86_64 Linux? George Neuner <gneuner2@comcast.net> - 2016-09-29 22:57 -0400
Re: Alternative C compilers on x86_64 Linux? Hans-Peter Diettrich <DrDiettrich1@netscape.net> - 2016-09-30 05:03 +0200
Re: Alternative C compilers on x86_64 Linux? BartC <bc@freeuk.com> - 2016-09-30 12:00 +0100
Re: Alternative C compilers on x86_64 Linux? Hans-Peter Diettrich <DrDiettrich1@netscape.net> - 2016-09-30 20:15 +0200
Re: Alternative C compilers on x86_64 Linux? BartC <bc@freeuk.com> - 2016-10-01 22:17 +0100
Re: Alternative C compilers on x86_64 Linux? BartC <bc@freeuk.com> - 2016-09-30 12:28 +0100
Re: Alternative C compilers on x86_64 Linux? BartC <bc@freeuk.com> - 2016-10-17 22:49 +0100
Re: Alternative C compilers on x86_64 Linux? George Neuner <gneuner2@comcast.net> - 2016-09-28 21:24 -0400
Re: Alternative C compilers on x86_64 Linux? George Neuner <gneuner2@comcast.net> - 2016-09-28 01:01 -0400
Re: Alternative C compilers on x86_64 Linux? arnold@skeeve.com (Aharon Robbins) - 2016-09-29 02:55 +0000
Re: Alternative C compilers on x86_64 Linux? arnold@skeeve.com - 2016-09-29 05:30 -0600
Re: Alternative C compilers on x86_64 Linux? arnold@skeeve.com (Aharon Robbins) - 2016-09-30 10:13 +0000
csiph-web