System/Interpreter/Bugs/DesignReqd

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Requests: Interpreter   Bugs: Interpreter

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These reports/requests require new features, but the Dictionary is insufficient to define correct behavior. Design work is needed.


+"0 incorrectly gives error when applied to cell of fills

   $ (i. 0 3) +"1 i. 0 2
|length error
|   $(i.0 3)    +"1 i.0 2
   $ (i. 0 3) +"+"1 i. 0 2
0

Apparently the test for length error is built into the + verb. But it doesn't follow the rules: + should be applied to a cell of fills, fail, and then use scalar numeric as the shape/type of the failed result. +"+ shows the correct behavior. -- Henry Rich <<DateTime(2012-12-23T22:21:30-0500)>>

Status: this may not be an error. A better definition of fill-cell processing is needed.


'' { empty y gives wrong shape

   $ '' { i. 0 3
0 3
   $ '' {"{ i. 0 3
0

0 is correct (fill-cell should be used, producing result of 0 $ ,: 0 { i. 0 3; but 0 { i. 0 3 fails, so 0 should be used; result shape 0). But { seems to treat '' the same as a: which would properly produce shape 0 3.

-- Henry Rich <<DateTime(2014-06-10T13:36:02Z)>>

Status: this may not be an error. A better definition of fill-cell processing is needed.



security level out of date

The foreign 9!:25, security level, is out of date. The Dictionary page for 9!: says (4495 586 qdoj 'dx009') :

9!:25 y

Security Level. The security level is either 0 or 1. It is initially 0, and may be set to 1 (and can not be reset to 0). When the security level is 1, executing Window driver commands and certain foreigns (!:) that can alter the external state cause a “security violation” error to be signalled. The following foreigns are prohibited: dyads 0!:n , 1!:n except 1!:40 , 1!:41, and 1!:42 , 2!:n , and 16!:n .

The errors are:

  1. There are no dyads 0!:n, and the monads 0!:n are not prohibited. (One can load a file from the filesystem using 0!:0<fn; though, nicely, one cannot display the contents of a file with 0!:011<fn.)
  1. The are 1!:n foreigns which are not dyads but are prohibited; notably, 1!:1.
  1. Moreover, the foreigns 1!:40, 1!:41, 1!:42 and (family) 16!:, don't exist. OTOH the foreigns 1!:43, 1!:44, 1!:45, and family 15!: do exist, and are not prohibited by security level (except for the 15!: family, which is).
  1. The wd commands are not prohibited (that is, the J engine still sends 11!:0 requests to the front end). Try 11!:0'qwd'[9!:25[1 in j.exe . Worse, try 11!:0 'wd winexec * DEL /F /Q some_important_file.

Analogous wording for current version of J:

9!:25 y


Security Level. The security level is either 0 or 1. It is initially 0, and may be set to 1 (and can not be reset to 0). When the security level is 1, executing Window driver commands and certain foreigns (!:) that can alter the external state cause a “security violation” error to be signalled. The following foreigns are prohibited: 0!:n with __display as in __ 0!:__01__n , __the foreigns__ 1!:n except 1!:4__3__ , 1!:4__4__, and 1!:4__5__ , 2!:n , and 1__5__!:n .

But even this language leaves something to be desired. J programmers may have more security concerns than it covers.

At the simplest, you might also consider prohibiting 0!:n entirely, and the entire 1!: family, including 43+i.3. The former allows one to read files from the host, and the latter provides potentially sensitive information about its structure. (Besides, why should a restricted user be allowed to change the working directory)?

For a more comprehensive solution, please see my custom security level request.

Applies to ( 'j601/2006-11-17/17:05';6;'jwin32' ) -: (9!:14'') ; (9!:12'') ; wd 'qwd' (This does not mean that the bug is restricted to this environment, only that it is the one I tested.)

Status: open

-- Dan Bron <<DateTime(2007-04-17T22:33:05Z)>>

Query and Set CWD are allowed when security level = 1

1!:43 (query CWD) and 1!:44 (set CWD) are allowed when security level = 1. Surely Set at least, and Query probably, should be blocked.

-- Henry Rich <<DateTime(2014-05-24T16:34:41Z)>>

Status: open.

2!:55 blocked when security level = 1

Leaving no way to exit.

-- Henry Rich <<DateTime(2014-05-01T16:23:05Z)>>

Status: open.

Incorrect shape in u/. applied to empty

   $ ]/. i. 2 4
5 2
   $ ]/. i. 1 4
4 1
   $ ]/. i. 0 4
0 0

The last shape should be 3 0.

-- Henry Rich <<DateTime(2014-11-18T02:23:02Z)>>

Status: open. The definition of what oblique means on an empty array has not been adumbrated. There is some appeal to making the shape 3 0 here, but since the structure of the result is lost, 0 0, which emphasizes that fact, has a claim.