[PATCH] posix_builtins: allow exporting a reaonly

[PATCH] posix_builtins: allow exporting a reaonly

[Martijn Dekker]

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POSIX_BUILTINS incorrectly prohibits exporting a readonly variable. All 
other POSIX shells allow this and there is nothing in the POSIX text[*] 
that says it's not allowed. The attached patch fixes this.

Thanks,

- M.

[*] 
http://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_22

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diff --git a/Src/builtin.c b/Src/builtin.c
index 73cfe7a..a75c4b2 100644
--- a/Src/builtin.c
+++ b/Src/builtin.c
@@ -2169,7 +2169,7 @@ typeset_single(char *cname, char *pname, Param pm, UNUSED(int func),
 	    !ASG_VALUEP(asg))
 	    on |= PM_UNSET;
 	else if (usepm && (pm->node.flags & PM_READONLY) &&
-		 !(on & PM_READONLY)) {
+		 !(on & PM_READONLY) && !(on & PM_EXPORTED)) {
 	    zerr("read-only variable: %s", pm->node.nam);
 	    return NULL;
 	}

Re: [PATCH] posix_builtins: allow exporting a reaonly

[Bart Schaefer]

On Wed, Apr 18, 2018 at 12:58 PM, Martijn Dekker <martijn@inlv.org> wrote:
> POSIX_BUILTINS incorrectly prohibits exporting a readonly variable. All
> other POSIX shells allow this and there is nothing in the POSIX text[*] that
> says it's not allowed. The attached patch fixes this.

I hope it's really that simple -- see thread about typeset -T and
read-only and resulting confusion, e.g. zsh-workers/42061 and
references.

Re: [PATCH] posix_builtins: allow exporting a reaonly

[Martijn Dekker]

Op 18-04-18 om 22:07 schreef Bart Schaefer:
> On Wed, Apr 18, 2018 at 12:58 PM, Martijn Dekker <martijn@inlv.org> wrote:
>> POSIX_BUILTINS incorrectly prohibits exporting a readonly variable. All
>> other POSIX shells allow this and there is nothing in the POSIX text[*] that
>> says it's not allowed. The attached patch fixes this.
> 
> I hope it's really that simple -- see thread about typeset -T and
> read-only and resulting confusion, e.g. zsh-workers/42061 and
> references.

I can't really find anything in that thread or its references that seems 
relevant.

Exporting readonly variables was already possible with POSIXBUILTINS 
off, so I don't see how it could harm anything to allow it with 
POSIXBUILTINS on.

Here is some more context than was provided by the patch. Note that all 
of this is only executed if POSIXBUILTINS is on.

     if (isset(POSIXBUILTINS)) {
         /*
          * Stricter rules about retaining readonly attribute in this case.
          */
         if ((on & (PM_READONLY|PM_EXPORTED)) &&
             (!usepm || (pm->node.flags & PM_UNSET)) &&
             !ASG_VALUEP(asg))
             on |= PM_UNSET;
         else if (usepm && (pm->node.flags & PM_READONLY) &&
                  !(on & PM_READONLY) && !(on & PM_EXPORTED)) {
             zerr("read-only variable: %s", pm->node.nam);
             return NULL;
         }
     }

As the comment says, that block applies stricter rules about retaining 
the readonly attribute for POSIXBUILTINS. I merely removed the 
restriction that readonly variables cannot be exported by adding:

	 && !(on & PM_EXPORTED)

Note that the restriction was already inconsistent: this code did not 
block unset readonly variables from being given the export flag.

FWIW, the test suite passes cleanly with this patch.

Thanks,

- M.

[PATCH] posix_builtins: allow exporting a readonly

[Martijn Dekker]

Op 18-04-18 om 20:58 schreef Martijn Dekker:
> POSIX_BUILTINS incorrectly prohibits exporting a readonly variable. All 
> other POSIX shells allow this and there is nothing in the POSIX text[*] 
> that says it's not allowed. The attached patch fixes this.

This seems to have been forgotten about, so I'm trying again.

To recap:

$ zsh -c 'readonly foo=123; export foo'			# OK
$ zsh --emulate sh -c 'readonly foo=123; export foo'	# BUG
zsh:1: read-only variable: foo

I had another look at it and I think this patch (attached) should be 
even more straightforward. It simply checks if we are running the 
'export' command and then reverts to normal behaviour instead of the 
special-casing for POSIXBUILTINS which is incorrect for this case.

Note that the patched code block is only executed with POSIXBUILTINS 
active so won't otherwise affect anything in any case.

Also, attempts to assign using 'export' still correctly error out with 
the patch, as they do on other shells:

$ zsh --emulate sh -c 'readonly foo=123; export foo=123'
zsh:1: read-only variable: foo

Thanks,

- M.

-- 
modernish -- harness the shell
https://github.com/modernish/modernish

Re: [PATCH] posix_builtins: allow exporting a readonly

[Peter Stephenson]

On Thu, 2019-06-20 at 19:47 +0100, Martijn Dekker wrote:
> Op 18-04-18 om 20:58 schreef Martijn Dekker:
> > 
> > POSIX_BUILTINS incorrectly prohibits exporting a readonly variable. All 
> > other POSIX shells allow this and there is nothing in the POSIX text[*] 
> > that says it's not allowed. The attached patch fixes this.
> This seems to have been forgotten about, so I'm trying again.
> 
> To recap:
> 
> $ zsh -c 'readonly foo=123; export foo'			# OK
> $ zsh --emulate sh -c 'readonly foo=123; export foo'	# BUG
> zsh:1: read-only variable: foo
> 
> I had another look at it and I think this patch (attached) should be 
> even more straightforward.

This sounds fine but I don't think there is an attachment.

pws

Re: [PATCH] posix_builtins: allow exporting a readonly

[Martijn Dekker]

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Op 21-06-19 om 09:59 schreef Peter Stephenson:
> On Thu, 2019-06-20 at 19:47 +0100, Martijn Dekker wrote:
>> Op 18-04-18 om 20:58 schreef Martijn Dekker:
>>>   
>>> POSIX_BUILTINS incorrectly prohibits exporting a readonly variable. All
>>> other POSIX shells allow this and there is nothing in the POSIX text[*]
>>> that says it's not allowed. The attached patch fixes this.
>> This seems to have been forgotten about, so I'm trying again.
>>   
>> To recap:
>>   
>> $ zsh -c 'readonly foo=123; export foo'			# OK
>> $ zsh --emulate sh -c 'readonly foo=123; export foo'	# BUG
>> zsh:1: read-only variable: foo
>>   
>> I had another look at it and I think this patch (attached) should be
>> even more straightforward.
> 
> This sounds fine but I don't think there is an attachment.

Woops. :-/

Here it is...

- M.

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diff --git a/Src/builtin.c b/Src/builtin.c
index 2453f82c0..e863cc4bb 100644
--- a/Src/builtin.c
+++ b/Src/builtin.c
@@ -2171,7 +2171,7 @@ typeset_single(char *cname, char *pname, Param pm, UNUSED(int func),
 	    !ASG_VALUEP(asg))
 	    on |= PM_UNSET;
 	else if (usepm && (pm->node.flags & PM_READONLY) &&
-		 !(on & PM_READONLY)) {
+		 !(on & PM_READONLY) && func != BIN_EXPORT) {
 	    zerr("read-only variable: %s", pm->node.nam);
 	    return NULL;
 	}