286259 - Regexp literal reuses old RegExp object

Status: RESOLVED DUPLICATE of bug 98409

(Core :: JavaScript Engine, defect)

Description

[Magnus Kristiansen]

User-Agent:       Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; .NET CLR 1.1.4322)
Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.5) Gecko/20041217

Regexp literal notation creates one global RegExp object and makes all use of 
the literal in repeated function calls refer to this one object. This 
makes .lastIndex, exec() and test() very unreliable.

Reproducible: Always

Steps to Reproduce:
1. Call a function including var a = /someregexp/ and store result.
2. Call the function again and compare local var with stored previous result.

or

1. Call a function including var a = /someregexp/g and alert the lastIndex, 
which is 0.
2. Call exec() or test() on the regexp at least once.
3. Call function again and notice the lastIndex alert is not 0.
(Calling enough times will return the lastIndex to zero and then restart the 
cycle, so in a few cases lastIndex becomes 0 after all.)
Actual Results:  
Mozilla reports they are === (the same RegExp object).
or
Mozilla reports that lastIndex is not 0.

Expected Results:  
Mozilla reports that they are not the same object.
or
Mozilla reports that lastIndex is 0.

I am aware that this behavior is according to the ECMA specification, but from 
a usage point of view it's unacceptable. When using 'var re = /regexp/;' in a 
function, the regexp should be (or at least seem to be) created and perish 
with the variable. When the object lives on and returns with repeated 
references as currently, lastIndex, test() and exec() are no longer 
trustworthy.

As the testcase shows, other literal object notations do not create global 
objects and act as references to it like regexp currently does.

Suggested fix: Make lastIndex reset to 0 every time a literal is accessed, or 
eventually create a new RegExp object each time.

Workarounds: Don't use regexp literal notation in functions that might be 
called more than once, or manually reset .lastIndex to 0 every time you 
reference a regexp literal.

Comment 1

[Brendan Eich [:brendan]]

Stop filing bugs in bugzilla.mozilla.org about what you regard as flaws in the
ECMA-262 (ISO-16262) spec.  Take it to ECMA, and try to address the
compatibility issue: how will all the deployments and implementations possibly
handle current ECMA and a future version that does what you want.

/be

Comment 2

[Matthias Versen [:Matti]]

verified invalid

Comment 3

[:Gavin Sharp [email: [e-mail]]]

*** This bug has been marked as a duplicate of 98409 ***