* Re: [9fans] Local variables and rc functions
@ 2008-08-14 14:32 Russ Cox
2008-08-14 18:10 ` Micah Stetson
0 siblings, 1 reply; 7+ messages in thread
From: Russ Cox @ 2008-08-14 14:32 UTC (permalink / raw)
To: 9fans
> Is this a bug?
>
> % fn foo { echo $bar }
> % bar=baz foo
>
> %
>
> I would expect to see baz instead of a blank line.
Yes, it is a bug. The fix is:
diff -r f7e7b9ab4cfb src/cmd/rc/simple.c
--- a/src/cmd/rc/simple.c Sun Jul 20 06:17:17 2008 -0400
+++ b/src/cmd/rc/simple.c Thu Aug 14 10:27:08 2008 -0400
@@ -130,7 +130,7 @@ execfunc(var *func)
starval = runq->argv->words;
runq->argv->words = 0;
poplist();
- start(func->fn, func->pc, (struct var *)0);
+ start(func->fn, func->pc, runq->local);
runq->local = newvar(strdup("*"), runq->local);
runq->local->val = starval;
runq->local->changed = 1;
There's also a small performance bug here:
diff -r f7e7b9ab4cfb src/cmd/rc/code.c
--- a/src/cmd/rc/code.c Sun Jul 20 06:17:17 2008 -0400
+++ b/src/cmd/rc/code.c Thu Aug 14 10:27:08 2008 -0400
@@ -339,9 +339,9 @@ outcode(tree *t, int eflag)
outcode(c0, eflag);
emitf(Xlocal);
}
- t = tt;
- outcode(c2, eflag);
- for(;t->type=='=';t = c2) emitf(Xunlocal);
+ outcode(t, eflag);
+ for(t = tt; t->type=='='; t = c2)
+ emitf(Xunlocal);
}
else{
for(t = tt;t;t = c2){
Both fixes are in plan9port.
Russ
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [9fans] Local variables and rc functions
2008-08-14 14:32 [9fans] Local variables and rc functions Russ Cox
@ 2008-08-14 18:10 ` Micah Stetson
0 siblings, 0 replies; 7+ messages in thread
From: Micah Stetson @ 2008-08-14 18:10 UTC (permalink / raw)
To: Fans of the OS Plan 9 from Bell Labs
> Both fixes are in plan9port.
Thanks, Russ.
Micah
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [9fans] Local variables and rc functions
2008-08-14 12:14 ` roger peppe
@ 2008-08-14 12:47 ` kazumi iwane
0 siblings, 0 replies; 7+ messages in thread
From: kazumi iwane @ 2008-08-14 12:47 UTC (permalink / raw)
To: Fans of the OS Plan 9 from Bell Labs
i apologize for the noise. i should have tested befoqe posting.
rog, thank you for correcting me.
On 8/14/08, roger peppe <rogpeppe@gmail.com> wrote:
> On Thu, Aug 14, 2008 at 12:20 PM, kazumi iwane <kiwane@gmail.com> wrote:
>> if you want to delay the expansion of an env var until fn invocation,,use
>> eval.
>>
>> % fn foo {eval echo $$bar}
>
> sorry, but that's so, so wrong.
>
> 1) $$bar gives the value of the variable
> named by the contents of the variable bar,
> so that the above, given that $bar contains 'baz'
> will echo $baz.
>
> 2) $$bar above is evaluated _before_ eval is invoked,
> so the line is not very different from {echo $$bar}, except that
> if $$bar holds any syntax characters they'll get interpreted by the shell.
> it's almost never necessary to use eval with rc.
>
> 3) expansion of env. vars *is* delayed until fn invocation.
> e.g.
> % fn foo {echo $bar}
> % bar = baz
> % foo
> baz
> %
>
> it just seems as if the local variable assignment isn't propagated
> into the fn context. i don't have time to look into it now (i really
> shouldn't be spending time writing this email, but i couldn't resist the
> bait).
>
> rog.
>
>
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [9fans] Local variables and rc functions
2008-08-14 11:20 ` kazumi iwane
@ 2008-08-14 12:14 ` roger peppe
2008-08-14 12:47 ` kazumi iwane
0 siblings, 1 reply; 7+ messages in thread
From: roger peppe @ 2008-08-14 12:14 UTC (permalink / raw)
To: Fans of the OS Plan 9 from Bell Labs
On Thu, Aug 14, 2008 at 12:20 PM, kazumi iwane <kiwane@gmail.com> wrote:
> if you want to delay the expansion of an env var until fn invocation,,use eval.
>
> % fn foo {eval echo $$bar}
sorry, but that's so, so wrong.
1) $$bar gives the value of the variable
named by the contents of the variable bar,
so that the above, given that $bar contains 'baz'
will echo $baz.
2) $$bar above is evaluated _before_ eval is invoked,
so the line is not very different from {echo $$bar}, except that
if $$bar holds any syntax characters they'll get interpreted by the shell.
it's almost never necessary to use eval with rc.
3) expansion of env. vars *is* delayed until fn invocation.
e.g.
% fn foo {echo $bar}
% bar = baz
% foo
baz
%
it just seems as if the local variable assignment isn't propagated
into the fn context. i don't have time to look into it now (i really
shouldn't be spending time writing this email, but i couldn't resist the bait).
rog.
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [9fans] Local variables and rc functions
2008-08-14 9:25 ` roger peppe
@ 2008-08-14 11:20 ` kazumi iwane
2008-08-14 12:14 ` roger peppe
0 siblings, 1 reply; 7+ messages in thread
From: kazumi iwane @ 2008-08-14 11:20 UTC (permalink / raw)
To: Fans of the OS Plan 9 from Bell Labs
if you want to delay the expansion of an env var until fn invocation,,use eval.
% fn foo {eval echo $$bar}
On 8/14/08, roger peppe <rogpeppe@gmail.com> wrote:
> looks like a bug to me; after all:
>
> % bar=baz {echo $bar}
> baz
> %
>
> i'm somewhat surprised this hasn't been fixed years ago.
>
> On Wed, Aug 13, 2008 at 10:27 PM, Micah Stetson <micah@stetsonnet.org>
> wrote:
>> Is this a bug?
>>
>> % fn foo { echo $bar }
>> % bar=baz foo
>>
>> %
>>
>> I would expect to see baz instead of a blank line.
>>
>> Micah
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [9fans] Local variables and rc functions
2008-08-13 21:27 Micah Stetson
@ 2008-08-14 9:25 ` roger peppe
2008-08-14 11:20 ` kazumi iwane
0 siblings, 1 reply; 7+ messages in thread
From: roger peppe @ 2008-08-14 9:25 UTC (permalink / raw)
To: Fans of the OS Plan 9 from Bell Labs
looks like a bug to me; after all:
% bar=baz {echo $bar}
baz
%
i'm somewhat surprised this hasn't been fixed years ago.
On Wed, Aug 13, 2008 at 10:27 PM, Micah Stetson <micah@stetsonnet.org> wrote:
> Is this a bug?
>
> % fn foo { echo $bar }
> % bar=baz foo
>
> %
>
> I would expect to see baz instead of a blank line.
>
> Micah
>
>
^ permalink raw reply [flat|nested] 7+ messages in thread
* [9fans] Local variables and rc functions
@ 2008-08-13 21:27 Micah Stetson
2008-08-14 9:25 ` roger peppe
0 siblings, 1 reply; 7+ messages in thread
From: Micah Stetson @ 2008-08-13 21:27 UTC (permalink / raw)
To: Fans of the OS Plan 9 from Bell Labs
Is this a bug?
% fn foo { echo $bar }
% bar=baz foo
%
I would expect to see baz instead of a blank line.
Micah
^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2008-08-14 18:10 UTC | newest]
Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
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2008-08-14 14:32 [9fans] Local variables and rc functions Russ Cox
2008-08-14 18:10 ` Micah Stetson
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2008-08-13 21:27 Micah Stetson
2008-08-14 9:25 ` roger peppe
2008-08-14 11:20 ` kazumi iwane
2008-08-14 12:14 ` roger peppe
2008-08-14 12:47 ` kazumi iwane
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