* [9fans] C99 and you
@ 2006-10-05 18:32 Skip Tavakkolian
2006-10-06 0:09 ` Bruce Ellis
0 siblings, 1 reply; 6+ messages in thread
From: Skip Tavakkolian @ 2006-10-05 18:32 UTC (permalink / raw)
To: 9fans
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somebody had a question a couple of days ago. i wonder if the declaration
was inside a switch or after a label?
in the example below, if the seemingly superfluous ';' (comments 1, and 2)
are removed, it is a syntax error. also note the scope of the declaration
inside a switch (e.g. when argc==1)
explanation: http://www.thescripts.com/forum/thread214730.html
reference: http://wwwold.dkuug.dk/jtc1/sc22/open/n2794/n2794.txt (look for A.2.3)
[-- Attachment #2: c99test.c --]
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#include <u.h>
#include <libc.h>
main(int argc, char **argv)
{
int i;
switch (argc) {
case 2:
; // 1
int j = 1;
print("argc = %d; j = %d\n", argc, j);
break;
case 1:
j = 0;
print("argc = %d; j = %d\n", argc, j);
break;
}
int k;
foo:
; // 2
int l;
exits(nil);
}
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [9fans] C99 and you
2006-10-05 18:32 [9fans] C99 and you Skip Tavakkolian
@ 2006-10-06 0:09 ` Bruce Ellis
2006-10-06 1:33 ` Skip Tavakkolian
2006-10-06 8:28 ` Charles Forsyth
0 siblings, 2 replies; 6+ messages in thread
From: Bruce Ellis @ 2006-10-06 0:09 UTC (permalink / raw)
To: Fans of the OS Plan 9 from Bell Labs
if that is the case i would suggest the grammar (yacc file) needs
a tweak - could be as simple as a missing case (or two).
good catch.
brucee
On 10/6/06, Skip Tavakkolian <9nut@9netics.com> wrote:
> somebody had a question a couple of days ago. i wonder if the declaration
> was inside a switch or after a label?
etc.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [9fans] C99 and you
2006-10-06 0:09 ` Bruce Ellis
@ 2006-10-06 1:33 ` Skip Tavakkolian
2006-10-06 8:28 ` Charles Forsyth
1 sibling, 0 replies; 6+ messages in thread
From: Skip Tavakkolian @ 2006-10-06 1:33 UTC (permalink / raw)
To: 9fans
> if that is the case i would suggest the grammar (yacc file) needs
> a tweak - could be as simple as a missing case (or two).
> good catch.
from what i understand, compiler is following the
spec. i don't know why the spec is that way.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [9fans] C99 and you
2006-10-06 0:09 ` Bruce Ellis
2006-10-06 1:33 ` Skip Tavakkolian
@ 2006-10-06 8:28 ` Charles Forsyth
2006-10-06 9:51 ` erik quanstrom
1 sibling, 1 reply; 6+ messages in thread
From: Charles Forsyth @ 2006-10-06 8:28 UTC (permalink / raw)
To: 9fans
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based on the grammar snippet posted earlier, it looks as though
the compiler is correct. a case label in C is not so different from a label
(thus duff's device is allowed), and as i understood the snippet,
declarations can't be labelled. might make you wonder why they
bothered, and indeed, i do wonder. i think they should leave the language alone.
(and if they were going to do more than tinker,
they might have added something significant, such as tuples.)
[-- Attachment #2: Type: message/rfc822, Size: 3269 bytes --]
From: "Bruce Ellis" <bruce.ellis@gmail.com>
To: "Fans of the OS Plan 9 from Bell Labs" <9fans@cse.psu.edu>
Subject: Re: [9fans] C99 and you
Date: Fri, 6 Oct 2006 10:09:20 +1000
Message-ID: <775b8d190610051709g5f9a66f5tc9c387315bc94d86@mail.gmail.com>
if that is the case i would suggest the grammar (yacc file) needs
a tweak - could be as simple as a missing case (or two).
good catch.
brucee
On 10/6/06, Skip Tavakkolian <9nut@9netics.com> wrote:
> somebody had a question a couple of days ago. i wonder if the declaration
> was inside a switch or after a label?
etc.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [9fans] C99 and you
2006-10-06 8:28 ` Charles Forsyth
@ 2006-10-06 9:51 ` erik quanstrom
2006-10-06 16:00 ` Bruce Ellis
0 siblings, 1 reply; 6+ messages in thread
From: erik quanstrom @ 2006-10-06 9:51 UTC (permalink / raw)
To: 9fans
actually, the switch statement here is a red herring. here's what kenc dislikes:
label: int assignment = 0;
so this will generate an error, too:
void
main(void)
{
begin: int j;
j = 0;
if(j>1)
goto begin;
exits("");
}
gcc is also unable to parse this production.
- erik
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [9fans] C99 and you
2006-10-06 9:51 ` erik quanstrom
@ 2006-10-06 16:00 ` Bruce Ellis
0 siblings, 0 replies; 6+ messages in thread
From: Bruce Ellis @ 2006-10-06 16:00 UTC (permalink / raw)
To: Fans of the OS Plan 9 from Bell Labs
sorry, i misunderstood the absurd standard, again.
brucee
On 10/6/06, erik quanstrom <quanstro@quanstro.net> wrote:
> actually, the switch statement here is a red herring. here's what kenc dislikes:
>
> label: int assignment = 0;
>
> so this will generate an error, too:
>
> void
> main(void)
> {
> begin: int j;
> j = 0;
> if(j>1)
> goto begin;
> exits("");
> }
>
> gcc is also unable to parse this production.
>
> - erik
>
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2006-10-06 16:00 UTC | newest]
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2006-10-05 18:32 [9fans] C99 and you Skip Tavakkolian
2006-10-06 0:09 ` Bruce Ellis
2006-10-06 1:33 ` Skip Tavakkolian
2006-10-06 8:28 ` Charles Forsyth
2006-10-06 9:51 ` erik quanstrom
2006-10-06 16:00 ` Bruce Ellis
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